Makita Bi-Metal Cup Saw Kit has an ejector/ejector spring that helps to remove the perforated material This bi-metal cup saw kit has a limiting base that minimizes the impact after the hole The bi-metal cup saw kit has indication for drilling in steel, metal, stainless steel, aluminum and non-ferrous metal plates This bi-metal cup saw kit aids in the removal of perforated material The bi-metal cup saw kit minimizes impacts after the hole This bi-metal cup saw kit has limiter absorbs the impact when the hole saw cuts through the materials