Fowlers preserving rings fit Fowlers preserving jars.
Size 1 rings fit old style Fowlers 1 pint fruit juice bottle.
Size 2 rings fit Fowlers jar numbers 3, 10 and 19.
Size 3 rings fit Fowlers jar numbers 14, 20 and 27.
Size 4 rings fit Fowlers jar number 31, 36 and 65.
If you are not sure what size Fowler jars you have measure the diameter of the jar opening. Size 3 rings fit jars that have a opening of 3 inch diameter and a size 4 rings fit jars that have a jar opening of 4 inch diameter.