JK Findings, Yellow Gold Filled Spring Ring Clasps, Ideal for Your Jewelry Making, 1/20 14K Gold Filled
Size: about 8mm long, 6mm wide, 1mm thick, hole: 1.5mm.
Gold filled uses a karat gold overlay which is then bonded to a brass inner core. JK Findings manufactures gold filled with 1/20th 14K gold, meaning, it is 5% karat gold by weight with a brass inner core.