The material is silicon
NSN 6105-01-338-6249
NSN 2925-00-925-0545
NSN 6610-01-618-7038
NSN 5975-00-019-4024
NSN 5996-01-542-0903
NSN 5990-01-349-8132
NSN 5915-01-469-3400
NSN 5930-01-413-2982
NSN 5990-00-212-4316
NSN 6320-01-326-1316
NSN 6105-01-259-6041
NSN 6650-01-230-1501