The smallest box S packs two 250g jars, the small box M fits perfectly for two 500g jars, the large L fits three 500g jars or four 250g jars. If you want to give yourself or others a year's supply of ten 500g jars, the XL box is a good choice.
Sfor 2x250g jars
M for 2x 500g jars
L for 3x 500g or 4x 250g jars
XL for a year's supply of 10x 500g jars