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LEGO Missing Piece Checker

Rule out the usual hiding places first. If the piece really is gone, check the set piece by piece and leave with the element ID LEGO asks for, or a link to buy the part.

Checking

7721 Combat Crawler X2

561 pieces in 156 part and color combinations, plus 3 minifigures.

The official piece count includes the 20 parts inside the set's minifigures, which this inventory lists separately. Spare parts are counted in neither figure.

Before you call it missing

Builders who report a missing piece often find it in one of these places. Tick each one off as you look.

Every bag and the box. Shake out each bag, check its corners and seams, and look inside the empty box.
Inside what you have built. Small pieces lodge inside tubes, under plates and between studs. Turn the model over and look.
The last few steps. Compare each recent step with its parts callout. A piece used in the wrong place earlier leaves you one short later.
Look-alike colors. 8 parts in this set come in two colors that are easy to mix up; they are listed below.
The spare pieces. This set comes with 16 spare pieces, marked on each row of the checklist. One may be the piece you need.
The floor and your building area. Check under furniture, the chair and the edges of your building surface.

Look-alike colors in this set

These parts appear in this set in two colors that are easy to confuse. If you are one short in one color, check whether it went in where the other color belongs. Each color has its own element ID in the parts list at the back of the instructions.

Windscreen 5 x 2 x 1 2/3 Black ×1 Trans-Brown ×1 Trans-Brown is see-through: hold the piece up to a light.
Brick 1 x 2 Black ×3 Dark Bluish Gray ×1 Black is darker than Dark Bluish Gray.
Plate 2 x 2 Black ×2 Dark Bluish Gray ×6 Black is darker than Dark Bluish Gray.
Plate 4 x 4 Black ×1 Dark Bluish Gray ×2 Black is darker than Dark Bluish Gray.
Plate Special 2 x 2 with 1 Pin Hole [Split Underside Ribs] Black ×1 Dark Bluish Gray ×7 Black is darker than Dark Bluish Gray.
Technic Brick 1 x 2 with Axle Hole Type 2 [X Opening] Black ×8 Dark Bluish Gray ×7 Black is darker than Dark Bluish Gray.

2 more look-alike pairs

Technic Plate 2 x 4 [3 Holes] Black ×6 Dark Bluish Gray ×8 Black is darker than Dark Bluish Gray.
Tile 2 x 2 with Groove Black ×1 Dark Bluish Gray ×1 Black is darker than Dark Bluish Gray.

Piece checklist

Technic Pins 104 pieces

Technic Pin Long with Friction Ridges Lengthwise, 2 Center Slots Black Part 6558 Element 655826 ×46
Technic Pin with Friction Ridges Lengthwise and Center Slots Black Part 2780 Element 4121715 or 278026 5 spares in the box ×33
Technic Rotation Joint Ball Loop with Two Perpendicular Pins with Friction Black Part 47455 Element 4272426 or 4213374 ×4
Technic Axle Pin with Friction Ridges Lengthwise Blue Part 43093 Element 4309323 or 4206482 ×9
Technic Pin 1/2 without Friction Ridges Light Bluish Gray Part 4274 Element 4274194 or 4211483 1 spare in the box ×2
Technic Pin Long with Friction Ridges Lengthwise and Stop Bush [3 Lateral Holes, Big Pin Hole] Red Part 32054 Element 4140806 or 4125198 ×6
Technic Axle Pin without Friction Ridges Lengthwise Tan Part 3749 Element 4666579 or 4186017 ×4

Technic Bricks 37 pieces

Technic Brick 1 x 14 [13 Pin Holes] Black Part 32018 Element 4107558 ×6
Technic Brick 1 x 2 with Axle Hole Type 2 [X Opening] Black Part 32064b Also in Dark Bluish Gray ×8
Technic Brick 1 x 6 [5 Pin Holes] Black Part 3894 Element 389426 ×2
Technic Brick 6 x 8 with 4 x 6 Opening Black Part 32532 Element 6448394 or 4188143 ×2
Technic Brick 1 x 2 with Axle Hole Type 2 [X Opening] Dark Bluish Gray Part 32064b Also in Black ×7
Technic Brick 1 x 4 [3 Pin Holes] Dark Bluish Gray Part 3701 Element 4213607 or 370127 ×2
Technic Brick 1 x 2 [1 Pin Hole] Light Bluish Gray Part 3700 Element 4211440 ×8
Technic Brick 1 x 2 [2 Pin Holes] Red Part 32000 Element 4179355 or 4101764 ×1
Technic Brick 1 x 2 with Axle Hole Type 2 [X Opening] Yellow Part 32064b ×1

Technic Axles 32 pieces

Technic Axle 10 Black Part 3737 Element 373726 ×2
Technic Axle 4 Black Part 3705 Element 370526 ×5
Technic Axle 6 Black Part 3706 Element 370626 ×1
Technic Axle 8 with Stop Black Part 55013 Element 4288089 ×2
Technic Axle 3 with Stud Dark Bluish Gray Part 6587 Element 6587199 or 6129590 ×8
Technic Axle 5.5 with Stop [Rounded Short End] Dark Bluish Gray Part 59426 Element 4508553 ×2
Technic Axle 3 Light Bluish Gray Part 4519 Element 4211815 ×4
Technic Axle 2 Notched Red Part 32062 Element 4142865 ×8

Technic Special 24 pieces

Technic Brick Special 2 x 2 with Pin Hole, with 2 Rotation Joint Sockets Black Part 48172 Element 6296186 or 4275826 ×1
Technic Disc 3 x 3 Black Part 2723 Element 4218868 or 4121619 ×2
Technic Link 1 x 5 Black Part 30397 Element 4140701 ×4
Technic Brick 1 x 2 - 1 x 2 Angled with Bumper Holder [Closed Front] Dark Bluish Gray Part 2991 ×4
Technic Brick Special 2 x 2 with 10.2mm Balls [Center Mold Indention] Dark Bluish Gray Part 57908 Element 4498096 ×1
Technic Brick Special 2 x 2 with Ball Socket Reinforced and Axle Hole Dark Bluish Gray Part 62712 Element 4524353 or 4497254 ×4
Technic Brick Special 2 x 2 with Pin Hole, Rotation Joint Ball Half [Vertical Side] Dark Bluish Gray Part 48171 Element 6492115 or 6343337 ×4
Technic Brick Special 2 x 2 with Pin Hole, Rotation Joint Socket Dark Bluish Gray Part 48169 Element 6278974 or 4225973 ×2
Technic Brick Special 2 x 2 with Solid Ball and Axle Hole Dark Bluish Gray Part 57909a ×2

Bricks 19 pieces

Brick 1 x 1 Black Part 3005 Element 300526 ×4
Brick 1 x 2 Black Part 3004 Element 300426 Also in Dark Bluish Gray ×3
Brick 2 x 4 Black Part 3001 Element 300126 ×2
Brick 2 x 6 Black Part 2456 Element 4181144 or 245626 ×2
Brick 1 x 2 Dark Bluish Gray Part 3004 Element 4211088 Also in Black ×1
Brick 1 x 2 x 2 with Inside Axle Holder Dark Bluish Gray Part 3245b ×2
Brick 1 x 3 Light Bluish Gray Part 3622 Element 4211428 ×4
Brick 1 x 6 Light Bluish Gray Part 3009 Element 4211393 ×1

Bricks Special 17 pieces

Brick Special 1 x 4 with 4 Studs on One Side Black Part 30414 Element 4162443 ×2
Brick Special 1 x 2 with Pin Dark Bluish Gray Part 2458 Element 4211087 ×8
Brick Special 1 x 2 with 2 Pins, Round Pin Holes Light Bluish Gray Part 30526 Element 4211660 ×5
Brick Special 1 x 1 with Headlight Red Part 4070 Element 407021 ×2

Bricks Round and Cones 16 pieces

Brick Round 1 x 1 with Fins, Open Stud Dark Bluish Gray Part 4588 Element 6331222 or 6321195 ×6
Brick Round 1 x 1 Open Stud Light Bluish Gray Part 3062b Element 4211412 ×2
Cone 1 x 1 [No Top Groove] Trans-Neon Green Part 4589 Element 618849 or 458949 ×6
Brick Round 2 x 2 with Axle Hole Yellow Part 3941 Element 614324 or 394124 ×2

Technic Bushes 15 pieces

Technic Bush 1/2 Smooth with Axle Hole Semi-Reduced Light Bluish Gray Part 32123b Element 6271165 or 4211573 2 spares in the box ×5
Technic Bush Red Part 3713 Element 6271820 or 4227155 3 spares in the box ×10

Bricks Wedged 14 pieces

Brick Wedged, Curved 16 x 4 Triple with Inner Ridges Black Part 45301 Element 4200486 ×6
Brick Wedged, Curved 6 x 2 Left, Inner Ridges White Part 41748 Element 6552117 or 4160124 ×1
Brick Wedged, Curved 6 x 2 Right, Inner Ridges White Part 41747 Element 4160101 ×1
Brick Wedged, Curved 4 x 4 No Top Studs Yellow Part 47753 Element 4639061 or 4294741 ×6

Large Buildable Figures 14 pieces

Large Figure Weapon, Claw Hook with Axle Light Bluish Gray Part 32551 Element 4234608 ×12
Large Figure Weapon Claw Blade, Small Red Part 57528 Element 4543162 or 4513223 ×2

Bricks Sloped 12 pieces

Brick Sloped 45° 2 x 1 Triple Smooth Black Part 3048b ×2
Brick Sloped 45° 2 x 3 Black Part 3038 Element 303826 ×2
Brick Sloped 45° 2 x 8 Black Part 4445 Element 4163334 ×2
Brick Sloped 75° 2 x 2 x 3 [Hollow Studs] Black Part 3684 Element 4286874 or 4248065 ×1
Brick Sloped 45° 2 x 2 Dark Bluish Gray Part 3039 Element 4211054 ×1
Brick Sloped Inverted 45° 2 x 1 Dark Bluish Gray Part 3665 Element 4211096 ×2
Brick Sloped Inverted 45° 2 x 2 [Ovoid Bottom Pin, Bar-sized Stud Holes] Dark Bluish Gray Part 3660 Element 4211000 ×1
Brick Sloped 45° 2 x 2 Yellow Part 3039 Element 303924 ×1

Hinges, Arms and Turntables 12 pieces

Hinge Panel 2 x 4 x 3 1/3 Locking Dual 2 Fingers Black Part 44572 Element 4193086 ×4
Turntable 4 x 4 Top, Locking Black Part 30658 Element 4142915 ×1
Hinge Plate 1 x 4 Locking Dual 1 Finger Light Bluish Gray Part 44568 Element 6276045 or 4211840 ×4
Turntable 4 x 4 Locking Grooved Base Light Bluish Gray Part 30516 Element 4296249 ×1
Hinge Plate 1 x 8 Locking with Angled Side Extensions, Rounded Plate Underside, 9 Teeth Yellow Part 30407 Element 4626523 or 4294480 ×2

Animal / Creature Body Parts 10 pieces

Animal Body Part, Barb / Claw / Tooth / Talon / Horn, Small Red Part 53451 Element 6270107 or 4568388 2 spares in the box ×10

Technic Gears 8 pieces

Technic Driving Ring Extension, 4 Ridges Light Bluish Gray Part 32187 Element 4278756 or 4209329 ×8

Bars, Ladders and Fences 7 pieces

Antenna 1 x 4 with Rounded Top Black Part 3957a ×2
Fence Spindled 1 x 4 x 2 [2 Top Studs] Dark Bluish Gray Part 30055 Element 4256495 ×3
Lever Small Base with Black Lever Yellow Part 298c02 Element 74156 1 spare in the box ×2

Minifig Upper Body 7 pieces

Arm Mechanical with 2 Clips [Battle Droid] Light Bluish Gray Part 30377 Element 6319333 or 4211658 1 spare in the box ×1
Arm Mechanical with Clip [Thin Support] Pearl Light Gray Part 53989 Element 4494600 or 4288114 ×6

Projectiles / Launchers 5 pieces

Launcher, Technic Competition Cannon Flat Bottom [Complete Assembly] Dark Bluish Gray Part 57796 Element 6064131 or 4518308 ×2
Projectile, Technic Competition Arrow, Liftarm Shaft with Hollow Black Rubber End Red Part 57028c01 Element 4504409 ×3

Tiles Special 5 pieces

Tile Special 1 x 2 Grille with Bottom Groove Black Part 2412b Element 241226 ×3
Tile Special 1 x 2 Grille with Bottom Groove Light Bluish Gray Part 2412b Element 4211350 ×2

Minifig Accessories 4 pieces

Tap 1 x 1 with Hole in Spout Light Bluish Gray Part 4599a ×4

Technic Beams Special 4 pieces

Technic Rotation Joint Disk with Pin Hole and 3L Beam Thick Dark Bluish Gray Part 44224 Element 4182751 ×2
Technic Rotation Joint Disk with Pin and 3L Beam Thick Light Bluish Gray Part 44225 Element 6671155 or 6332151 ×2

Tiles 4 pieces

Tile 2 x 2 with Groove Black Part 3068b Element 306826 Also in Dark Bluish Gray ×1
Tile 2 x 2 with Groove Dark Bluish Gray Part 3068b Element 4211055 Also in Black ×1
Tile 1 x 4 with Groove Red Part 2431 Element 243121 ×1
Tile 1 x 2 with Engraved Code for Exo-Force Yellow Part 3069bpr0073 Element 4513198 or 4507020 ×1

Plates Round Curved and Dishes 3 pieces

Plate Round 2 x 2 with Axle Hole Type 1 (+ Opening) Red Part 4032a Element 403221 ×1
Plate Round 1 x 1 with Solid Stud Trans-Red Part 6141 Element 6514051 or 6208450 1 spare in the box ×2

Bricks Curved 2 pieces

Brick Arch 1 x 6 x 2 - Thick Top with Reinforced Underside Black Part 3307 Element 330726 ×2

Energy Effects 2 pieces

Wave / Flame Rounded with Base Pegs Trans-Neon Orange Part 6126a ×2

Tubes and Hoses 2 pieces

Hose, Ribbed 7mm D. 11L / 8.8cm Pearl Light Gray Part 78c11 Element 4495208 or 4141672 ×2

Windscreens and Fuselage 2 pieces

Windscreen 5 x 2 x 1 2/3 Black Part 6070 Element 6252515 or 6170820 Also in Trans-Brown ×1
Windscreen 5 x 2 x 1 2/3 Trans-Brown Part 6070 Element 4204624 Also in Black ×1

Minifig Shields, Weapons, & Tools 1 piece

Tool Hammer / Mallet Large Black Part 4522 Element 452226 ×1

Stickers 1 piece

Sticker Sheet for Set 7721-1 [No Color/Any Color] Part 60491 Element 4512827 ×1

Supports, Girders and Cranes 1 piece

Crane Section 4 x 12 x 3 with 8 Pin Holes Black Part 52041 Element 4513143 ×1

Transportation - Land 1 piece

Handlebars Light Bluish Gray Part 30031 Element 4258308 ×1

Minifigures 3 figures

Ryo in Gold Armor Minifigure, checked as a whole figure ×1
Iron Drone / Devastator with Red Eyes Minifigure, checked as a whole figure ×1
Devastator with Trans-Red Torso and Red Eyes Minifigure, checked as a whole figure ×1

Tick each piece as you find it, or mark it missing.

When a piece really is missing

Ask LEGO

LEGO takes requests for pieces missing from a new set through its customer service site. The form asks for the set number and each piece's element ID, the number printed beside the piece in the parts list at the back of the instructions. This checker lists both.

Request a replacement from LEGO

Buy the piece

Mark a piece missing and your list links it to an eBay search for that part, which also covers pieces from older or second-hand sets.

Keep a record

Copy or download your missing list (the CSV opens in any spreadsheet), or print the whole checklist and tick pieces off on paper. Your marks stay in this browser, so you can check a big set over several sittings.