Also called internal expansion anchor. It is an internally threaded expansion sleeve with a built-in conical plug. After placing the anchor into pre-drilled solid concrete hole, use a setting tool to drive the cone downward, forcing the slotted sleeve to expand and lock tightly against the hole wall. Flush mounting, no protruding bolt. Matched with metric hex bolts or threaded rods. Available in carbon steel and 304 stainless steel, widely used for suspended ceilings, pipeline supports, electrical installations and construction fixtures.