a Aviation Aircraft Oxygen Valve Lapping tool. This one has been cleaned for oxygen service and unfortunately I cannot open the package or the clean rating will be lost so it did not take a good picture. If you need this you know what it is. PN# AS100070 NSN# 5120-01-276-3936 Thiis is a great buy You also get Better act because this won't last long Save $$$$$$$ here L2C5 10324