Aluminum head peen, 3" long. This versatile tool is great for forming sheet metal, driving pins, loosening bolts, etc. Works just like a mallet, but with a lot more control. Fits into any standard rivet gun or air hammer that supports .401" shank tooling. Replacement Brass (p/n ATS107-B), Aluminum (p/n ATS107-A), and Nylon (p/n ATS107-N) heads are available.