The material is silicon
NSN 6135-01-342-3859
NSN 6610-01-431-3371
NSN 6105-01-225-2077
NSN 6110-01-207-4543
NSN 5915-00-153-0002
NSN 6645-01-252-8870
NSN 5998-01-043-7535
NSN 6110-01-538-9762
NSN 5910-01-349-0825
NSN 5855-01-473-2904
NSN 5985-01-433-4024
NSN 6650-00-463-1514