It's a bullet anchor fastener. These anchors are also called as drop-in anchors. These anchors are a female concrete anchor. These anchors are specially designed for anchoring into concrete.These anchors are dropped into a pre-drilled hole of concrete. After that, using a setting tool anchor within the hole in the concrete should be expanded. These products are internally threaded, which allows the mounting hardware to be removed easily while leaving the anchor in place. It is also called as hammer set anchor. It is used for overhead hangers with threaded rod, handrails, shelving, light fixture, machinery, and others.