Size systems define the sizes your products run in. Each system holds one or more versions, and a version is either a flat list of sizes or a two-dimensional matrix for sizes that vary on two axes.

Click Add size system to create a system, it will create one in the bottom of the page, give it a name, and Save. A system holds its sizes as one or more versions — click Add version and name it. You can drag the versions to order them.

Open a version (the arrow on its row) to add and edit its sizes and then press save.

By default a version is a flat size range. Click Add size for each size; name the size and add a code if needed (system will create one shown in light grey when saved). Mark one size as the sample size with its star (used for m-list), Drag sizes to reorder or remove them with the trash icon.

For sizes that run on two axes — for example a waist and an inseam — tick 2D (matrix) on the version. The size range becomes a size matrix: fill the axes with + Col and + Row, and then click + within the matrix to get the sizes added.
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If you have a flat size range that you change to 2D (matrix) the system try to re-calculate and add your sizes in a matrix. Any sizes not possible to position, moves to Unplaced sizes until you position them. If no sizes are positioned, place one size in the matrix first to set the naming format, then use Auto-place by name (magic wand) to drop the rest into their cells automatically — or drag each size onto its cell by hand.

A version can also carry default sizes, set per gender (recommended to add).

When a product is created with a given gender, that gender's default sizes are applied automatically — You can always change them later on the product or article.