The material is silicon
NSN 6620-01-476-7355
NSN 4140-01-377-5828
NSN 6135-01-625-0765
NSN 6135-01-534-3007
NSN 5965-01-327-9234
NSN 6685-00-389-7935
NSN 6320-00-098-2858
NSN 2925-01-602-1975
NSN 5998-01-538-5026
NSN 5975-00-915-7632
NSN 6645-00-887-0122
NSN 2925-01-288-2091