Sort on size for customers

Store Design
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1

Have a store that is to be moved to shopify but need to make it so that you can sort by pearl size. See there is meta field for color which is good but how do I create new one for size in mm?

2

Thanks, the problem is that this meatfield dont show up in the filter.

3

Thanks, the problem is that this meatfield dont show up in the filter.

4

Found the problem, not all values are accepted in the filter-app.