The material is silicon
NSN 5855-00-451-6155
NSN 6240-01-610-6150
NSN 6130-01-105-4663
NSN 5835-01-385-0579
NSN 5910-00-248-4914
NSN 5855-00-951-6483
NSN 6105-00-138-9265
NSN 5965-01-039-1430
NSN 4140-01-313-3733
NSN 6240-01-474-3039
NSN 6240-01-543-9591
NSN 6150-01-400-4211