Free tool

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.

4.5V Reversible Power Unit

Checking

107-3 4.5V Reversible Power Unit

24 pieces in 9 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.

Show

Piece checklist

Wheels and Tyres 16 pieces

  • Tyre Smooth Old Style - Small Black Part 132a ×4
  • Tyre for Train Wheel for Electric Train Motor 12V Light Gray Part 458 ×4
  • Train Wheel with 2 x 2 Stud Center, Beveled Tread and Cam Axle for Motor Red Part upn0384b ×4
  • Wheel Old with 4 Studs and Axle Cam for Motor Red Part 7039b ×4

Electronics 7 pieces

  • Battery Box, 4.5V 7 x 11 x 3 Type 1 [Complete Assembly] Blue Part 468c01 ×1
  • Electric Connector, 1 Way Male Rounded with Hollow Pin (Banana Plug) Blue Part 996ac01 ×4
  • Motor, Train, 4.5V 12 x 4 x 4 Type I with '4.5V' Print Blue Part upn0284c02pr0001 ×1
  • Wire 12V / 4.5V with Two Leads [Undetermined Length] White Part 74503 ×1

Plates Special 1 piece

  • Plate Special 6 x 16 with Motor Opening Wide Light Gray Part 3058b ×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.