KaShDa Antiqued Copper Plated 4MM Curb Chain Necklace Extender Double 12MM Lobster Claw Clasp 1"-12" Adjustable length extender your choice of lengths from 1" to 12" including the clasp. 4MM Antiqued Copper Plated Brass Core Curb Chain with links that will accept clasps up to 3MM wide 12MM (1/2") Antiqued Copper Plated Brass Core Superior Quality Lobster Claw Clasps. Easy to move from one piece of jewelry to another. For jewelry pieces weighing up to 15 ounces. The only difference between the lengths is the length of the chain.