Hexagon head internal expansion screw (also often called internal explosion expansion bolt, hexagon head expansion bolt) is a type of expansion fastener, mainly used for the fixed installation on hard substrates such as concrete and brick walls.

It combines the convenient force application characteristic of the hexagon head with the fastening principle of internal expansion. When the hexagon head is tightened, the screw rod pulls the expansion tube to expand, forming a tight bite with the substrate. Its fixing strength is much higher than that of ordinary expansion screws. It is widely used for wall fixing of heavy objects such as guardrails, air conditioning outdoor units, shelves, and mechanical equipment. The common materials are 304/316 stainless steel or carbon steel with galvanizing, which are suitable for different corrosion resistance and load-bearing requirements.