KaShDa 1 1/4" - 12" Silver Plated Double 12MM Lobster Claw Chain/Necklace Extender 12MM (1/2") Silver Plated Brass Core Superior Quality Double Lobster Claw Clasps. 3.7MM Silver Plated Brass Core Curb Chain. Easy to move from one piece of jewelry to another. Use on chains or necklaces. Use with your chunky necklaces, these are strong enough to hold jewelry pieces weighing up to 15 ounces. The olny difference between the lengths is the length of the chain.