This 6-piece impact driver bit set is designed for use with air hammer guns. It includes a small fastener remover with 5/16in. hex impact bits. The set contains Ph1, Ph2, Ph3, Ph4, and an 8mm slotted bit. A 19mm or 3/4in. open-end spanner can be used to turn the bit holder while impacting the fastener. It works faster than hand impact tools and is especially useful for removing seized brake rotor screws.