Stainless steel 2BA socket cap screws. Upto and including 1" length are fully threaded. The 1/2", 9/16" and 5/8" lengths we actually make ourselves here in the UK, so these lengths have a smooth head, the rest have a knurling on the head. We make those lengths ourselves because they simply aren't available literally anywhere else in the world! Don't forget to checkout our other fasteners. Thank you.