We are specialized in all various kinds of extension springs.We can offer you samples free after you accept our price. We are specialized in all various kinds of extension springs:1). Wire diameter from 0.1mm-10mm.2). Material: carbon spring steel, alloy spring steel, stainless spring steel, etc.3). Finish: black oxide, zinc/nickel/chrome plating, power coating, passivate, oiled to prevent rust, ...