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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

42171 Mercedes-AMG F1 W14 E Performance

1,642 pieces in 217 part and color combinations.

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 31 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.

Technic Axle and Pin Connector Perpendicular Black ×14 Dark Bluish Gray ×2 Black is darker than Dark Bluish Gray.
Technic Beam 1 x 2 Thick with Pin Hole and Axle Hole Black ×8 Dark Bluish Gray ×4 Black is darker than Dark Bluish Gray.
Technic Beam 1 x 3 Thick Black ×7 Dark Bluish Gray ×2 Black is darker than Dark Bluish Gray.
Technic Beam 1 x 5 Thick Black ×5 Dark Bluish Gray ×1 Black is darker than Dark Bluish Gray.
Technic Beam 1 x 5 Thin with Axle Holes on Ends Black ×14 Dark Bluish Gray ×1 Black is darker than Dark Bluish Gray.
Technic Beam 1 x 7 Thick with Alternating Holes Black ×5 Dark Bluish Gray ×2 Black is darker than Dark Bluish Gray.

2 more look-alike pairs

Technic Driving Ring Connector Smooth [2 rounded and 2 flat side walls] Black ×2 Dark Bluish Gray ×4 Black is darker than Dark Bluish Gray.
Technic Pin Connector Hub with 1 Pin with Friction Ridges Lengthwise [Centered Friction Ridge] Black ×8 Dark Bluish Gray ×2 Black is darker than Dark Bluish Gray.

Piece checklist

Technic Bushes 37 pieces

Technic Bush Black Part 3713 Element 6332148 or 6210506 1 spare in the box ×3
Technic Bush Light Bluish Gray Part 3713 Element 6275844 or 6271817 1 spare in the box ×14
Technic Bush 1/2 Smooth with Axle Hole Semi-Reduced Light Bluish Gray Part 32123b Element 6271165 or 4211573 2 spares in the box ×17
Technic Bush Red Part 3713 Element 6271820 or 4227155 1 spare in the box ×2
Technic Bush 1/2 Smooth with Axle Hole Semi-Reduced Yellow Part 32123b Element 6271167 or 3212324 1 spare in the box ×1

Technic Beams Special 17 pieces

Technic Beam 3 x 0.5 Liftarm with Boss and Blocked, Squared Pin Hole Black Part 61408 Element 6313520 ×2
Technic Beam 3 x 5 Thick [90° Offset Centre Beam Holes] Black Part 14720 Element 6390379 ×2
Technic Beam Frame 3 x 19 with 2 Center Cross Beams, 3 Openings Thick Black Part 67491 Element 6377025 ×6
Technic Beam Frame 7 x 11 Black Part 39794 Element 6265643 ×2
Technic Beam 3 x 5 Thick [90° Offset Centre Beam Holes] Light Bluish Gray Part 14720 Element 6055519 ×2
Technic Beam 5 x 11 with 3 x 5 Opening Frame Thick Light Bluish Gray Part 64178 Element 4540797 ×1
Technic Beam 3 x 0.5 Liftarm with Boss and Blocked, Squared Pin Hole Red Part 61408 Element 6331864 ×2

Technic Gears 17 pieces

Technic Gear 12 Tooth Double Bevel Black Part 32270 Element 4177431 ×3
Technic Gear Rack 1 x 7 with Axle and Pin Holes Black Part 87761 Element 6327430 or 4562009 ×1
Technic Gear 8 Tooth [Reinforced] Dark Bluish Gray Part 10928 Element 6631413 or 6012451 ×4
Technic Gear Differential with Inner Tabs and Closed Center, 28 Bevel Teeth [Beveled Edge] Dark Bluish Gray Part 62821b Element 4562210 or 4525184 ×1
Technic Gear 12 Tooth Bevel Tan Part 6589 Element 4565452 or 4514556 ×5
Technic Gear 20 Tooth Double Bevel with Axle Hole Type 1 [+ Opening] Tan Part 18575 Element 6346517 or 6084724 ×3

Wheels and Tyres 12 pieces

Tyre 81.6 x 44 Slick Black Part 4410 Element 6475469 ×4
Wheel 56 x 34 Technic Racing Medium with 6 Pin Holes Black Part 15038 Element 6284703 or 6253256 ×4
Wheel Cover for Wheel 34 x 56 Black Part 4472 Element 6452871 ×4

Tiles 11 pieces

Tile 1 x 1 with Groove Black Part 3070b Element 307026 1 spare in the box ×1
Tile 1 x 2 with Groove Black Part 3069b Element 306926 ×2
Tile 1 x 6 with Groove Black Part 6636 Element 663626 ×2
Tile 1 x 8 with Groove Black Part 4162 Element 416226 ×4
Tile 2 x 3 Black Part 26603 Element 6162892 ×2

Bricks Round and Cones 7 pieces

Brick Round 1 x 1 diameter Tube with 90 Degree Elbow (2 x 2 x 1) and Axle Holes (Crossholes) at each end Black Part 25214 Element 6179182 ×1
Brick Round Curved 1 x 1 x 1 1/3 Quarter Dome Black Part 1871 Element 6436425 ×2
Brick Round 1 x 1 diameter Tube with 90 Degree Elbow (2 x 2 x 1) and Axle Holes (Crossholes) at each end Red Part 25214 Element 6176298 ×4

Tiles Round and Curved 7 pieces

Tile Round 1 x 1 with Bright Green Center Circle, White Print Black Part 98138pr0385 Element 6463207 1 spare in the box ×4
Tile Round 1 x 1 Dark Bluish Gray Part 98138 Element 6284596 or 6222416 1 spare in the box ×1
Tile Round 1 x 1 Half Circle Trans-Red Part 24246 Element 6507960 or 6264033 1 spare in the box ×2

Plates 5 pieces

Plate 1 x 1 Black Part 3024 Element 302426 1 spare in the box ×2
Plate 1 x 2 Black Part 3023 Element 302326 ×3

Bars, Ladders and Fences 4 pieces

Light Cover with Internal Bar / Bionicle Barraki Eye with Hole in Bar Black Part 4278 Element 6448948 1 spare in the box ×2
Bar 2L with Stop in Center Red Part 78258 Element 6399645 1 spare in the box ×2

Hinges, Arms and Turntables 4 pieces

Hinge Cylinder 1 x 2 Locking with 2 Click Fingers and Axle Hole, 7 Teeth Black Part 57360 Element 6271535 ×2
Hinge Plate 1 x 2 Locking with 1 Finger On End, without Groove Black Part 44301b Element 6266224 ×2

Plates Special 4 pieces

Plate Special Round 2 x 2 with Center Stud (Jumper Plate) Bright Green Part 18674 Element 6380676 ×4

Bricks Curved 3 pieces

Brick Curved 1 x 2 x 1 1/3 with Curved Top Black Part 6091 Element 6383142 or 6184784 ×1
Brick Curved 4 x 1 No Studs [Stud Holder with Symmetric Ridges] Black Part 11153 Element 6580394 or 6037746 ×2

Bricks Sloped 2 pieces

Brick Sloped 30° 1 x 1 x 2/3 (Cheese Slope) Black Part 54200 Element 4504382 or 4287159 1 spare in the box ×2

Plates Round Curved and Dishes 2 pieces

Plate Special 1 x 3 Rounded with 3 Open Studs Black Part 77850 Element 6428168 ×1
Plate Round 1 x 1 with Solid Stud Light Bluish Gray Part 6141 Element 4211525 1 spare in the box ×1

Stickers 2 pieces

Sticker Sheet 1 for Set 42171-1 [No Color/Any Color] Part 10105327 Element 6462840 ×1
Sticker Sheet 2 for Set 42171-1 [No Color/Any Color] Part 10107470 Element 6478964 ×1

Technic Bricks 2 pieces

Technic Pin Connector Block 1 x 5 x 3 Black Part 32333 Element 6271358 or 4141810 ×2

Technic Special 2 pieces

Technic Tooth 1 x 3 with Axle Hole [Hollow Underside] Black Part 48267 Element 6288220 ×2

Minifig Shields, Weapons, & Tools 1 piece

Weapon Spike Flexible 3.5L Black Part 64727 Element 6270085 or 6173917 ×1

Tubes and Hoses 1 piece

Axle Hose, Soft 19L Black Part 32235 Element 6139205 or 4121650 ×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.

LEGO Missing Piece Checker

42171 Mercedes-AMG F1 W14 E Performance

Before you call it missing

Look-alike colors in this set

Your missing list

Piece checklist

Technic Pins 593 pieces

Technic Beams 282 pieces

Technic Connectors 243 pieces

Technic Axles 179 pieces

Technic Panels 143 pieces