Item Number

Every item in the BrickLink catalog has an assigned number. For parts, that number usually appears somewhere on the part. For sets and other items, the number may appear on the box, or in a catalog. If a number is not known, then a number is created. Each item type uses different numbering format. Please note that this is not an exhaustive list of all Item Number formats, and that this page serves as a descriptive rather than a prescriptive definition of usage.
Naming Convention:
{ Base Part No. }{ Mold Variant }{ Pattern Constant }{ Pattern Sequential No. }{ Assembly Constant }{ Assembly Sequential No. }

3070; 3070p01; 3070apb01; 3070bpb01; 3070bp01
973; 973pb10; 973pb10c01

Part When Used Description
Base Part No. Always The part number is typically molded somewhere on the part. Some parts may have single and double digit numbers molded on them but these are not the part number. Molded part numbers will be 4 or 5 digits long. If part number does not exist then BrickLink uses a bb constant and uses an x constant. In some cases, BrickLink uses a descriptive number, for example 'door'.
Mold Variant Only if same part exists with different type of mold The oldest or original variant is given "a", the next "b", and so forth. For parts originally known to exist in only one mold type, if a pre-existing variation is discovered, it is given suffix "a", while a newly produced variation is given suffix "b".
Only if a part has a decorated pattern
  • pb - pattern constant
  • px - pattern constant
  • p - pattern constant
Pattern Sequential No. Only if a part has a decorated pattern Starts with 01, 001 or 0001 and is incremented by 1 for different decorated patterns used on the same part. Look up the highest used number and then use the next number.
Assembly Constant Only if a part is an assembly (if it consists of 2 or more parts) c is always used as a constant for part assemblies.
Assembly Sequential No. Only if a part is an assembly (if it consists of 2 or more parts) Start with 01 and increment by 1 for different color combinations of parts which are used to make up the part assembly.


  • Minifig, Torso Assembly - Pattern Constant and Sequential No. are placed before Assembly Constant and Sequential No. The first component of the assembly name refers to the pattern on the torso and the following components refer to colors of the arm and hand parts.

  • Minifig, Legs Assembly - If color of both legs is the same but not same as the hip color then an Assembly Constant of "c" is followed by a color ID as listed in the Color Guide. If color of both legs and hips are the same color then, the constant "c" is followed by the number "00". If 2 legs are in different colors or are not paired left and right leg parts, an Assembly Constant of "d" is used. Pattern numbers are used in sequence for each specific assembly. In other words a "pb01" on "c07" may not be the same pattern as a "pb01" on "c11".


 When adding a new part to the catalog or renaming an existing part number to a new part number, always use bb or descriptive name for base part number and pb for pattern constant. Unless you have taken your submission information directly from another site, do not use the constant for that site. Otherwise, 'collision' could occur with different websites using the same part number for different parts.

Naming Convention:
{ Set No. }{ Constant }{ Sequential No. }

6067stk01; 6067stk02

A sticker is assigned a number corresponding to the set in which it appears. If it appears in more than one set then it will have a separate catalog entry for each of those sets. For example, 5875stk01 and 5876stk01 are distinct catalog entries for the same sticker because it is found in sets 5875 and 5876.

If 2 sets have the same number then the set's sequential number such as 2 will be reflected in the sticker number as ".2". For example, 4032.1stk01 is a sticker for set 4032-1 and 4032.5stk01 is a sticker for set 4032-5.

Part When Used Description
Set No. Always is the LEGO assigned number of the set that the sticker comes in.
Designator Sometimes sequential number of set. "-2", is added here as ".2" if 2 or more sets with the same number exist.
Constant Always is always stk for stickers.
Sequential No. Always start with 01 and increment by 1 for multiple stickers in the same set.
Use the LEGO set number written on the box or instruction manual of most sets. LEGO has duplicated some set numbers. If you are adding a set to the catalog and another set with the same number is already in the catalog, then use the sequential number available. If a set doesn't have a set number printed on it, then use a descriptive text number, similar to parts.

Note: Some very old sets have a slash (/) in the item number. Since having the slash in the item number would cause a problem when linking to the catalog page for that set, use a period (.) in place of the slash when numbering these sets.

Naming Convention:
{ Series No. }{ Sequential No. }{ Variant }

s001; sw073; sw073a; 4j015; cas179; spp010; boat004; firec016

Part When Used Description
Series No. Always This is a custom number series developed by BrickLink. These initial characters are letters (and on occasion, a number) representing the theme, subtheme, or distinguishing features of the minifig. The distinguishing feature used for this purpose is often the torso pattern. Should be 2 or 3 letters.
Sequential No. Always Starts with 001 and is incremented by 1. To create a number for a new minifig, look at a currently listed figure from the same theme or subtheme, or with the same distinguishing feature. Find the Series No. code, then use the next available 3-digit number.
Variant Sometimes A letter used to indicate some difference from a minifig already carrying a particular Series and Sequential number. The primary minifig will not have this character and the first variant will usually be indicated with "a", the second with "b", and so on. "s" is used instead on a minifig with a stickered torso which has the same number as the same minifig without the sticker.
Use the book number where available. Idea Books always have a number on the book. Other types of books may have a number printed on them, listed in a catalog or have an official LEGO item number or ISBN number. LEGO item numbers are preferred over ISBN numbers. If no number is known, then use a descriptive text number, similar to parts.
Naming Convention:
{ Catalog Type }{ Year Code }{ Suffix }

s87eu; s95nz; m76us; m91pirate2; c66ch; c84cadc; c99asia; 4103360

Part When Used Description
Catalog Type Always This is a custom series developed by BrickLink. There are three possibilities: c = general catalog, m = mini catalog, and s = service packs catalog
Year Code Always This is invariably a 2-digit code representing the final 2 digits of a 4-digit year. For example, 2001 is represented by "01". This year should match with the Item Year, Item Category, and Item Name fields.
Suffix Always A group of letters or numbers representing region, theme, catalog subtype, etc. This is a free-form section with very few rules. However, any regional codes should be standardized, e.g. Germany should always be represented by "de".


  • Inserts - These are considered by some collectors to not be true catalogs, but they have been retained under the Catalogs Item Type so as to not clutter up the Books Item Type. They will often use the catalog code (which in the period of inserts was a 7-digit numeral) as the Item Number.

Item Number Restrictions:
  • Limit 15 characters.
  • Can only contain letters (A-Z), numbers (0-9), Dash (-), Period (.), and Underscore (_).