Used on nsn: 2420-01-532-3399. 21.0mm hole diameter washer, heat treated 54 dia thicknessmm 4; material ms 450 - 4140h; required 2 zinc surface treated
Used on 4520-01-477-0568; heater, duct type, portable. 3b thread class right-hand flat head style 18 thread quantity per inch flat head rivnut fastener