These Cobra® Drop-In anchors are a two-step installation anchors that expand using a setting tool. Made of sturdy steel, they are designed for medium duty of 530 lb maximum. They require a drill size of 3/8" and a minimum embedment of 1". It has female internal thread that accepts standard UNC threaded rods from 1/4" to 3/4". Sold in packs of 4 anchors.