Understanding Design IDs, Element IDs, Color Codes, and mold sub-variants. Learn how to locate numbers stamped inside your bricks and search official catalog databases.
Enter any 4-digit Design ID (e.g., 3001), 6-digit Element ID (e.g., 300121), or part name into our catalog engine.
The 4 or 5-digit number representing the physical shape of a piece, independent of its color or print.
The exact 6 or 7-digit identification code representing a specific Design ID in a specific color.
Letters appended to part numbers (e.g. 3068a vs 3068b) indicating subtle mold modifications over time.
Understanding catalog cross-references across LEGO Group, BrickLink, Rebrickable, and LDraw.
When LEGO casts plastic into a steel mold, the mold cavity has a small raised number engraved inside. For example, if you turn over a standard 2x4 red brick, you will see a small 4-digit number like 3001 between the anti-stud tubes. This number identifies the physical shape of the brick regardless of color.
LEGO’s internal inventory system tracks every single unique component with a 6-digit or 7-digit Element ID. For example:
When a piece receives a surface print (such as a dashboard print on a 2x2 slope or a torso print on a minifigure), the underlying plastic brick retains its base Design ID, but receives a secondary print code in catalog databases (e.g. 3039p01 or 973pb0123).
Very small pieces (like 1x1 studs, flowers, minifigure hands, and thin antenna rods) often lack physical room for stamped digits. If your piece has no readable numbers, use our AI Photo Identifier or Visual Piece Finder to recognize the piece instantly by photo or stud dimensions!