The material is silicon
NSN 6150-00-336-8171
NSN 6610-01-415-1623
NSN 5985-00-448-7035
NSN 6320-00-160-0899
NSN 6145-01-103-3273
NSN 6105-01-463-8557
NSN 6610-00-989-8912
NSN 6105-01-484-8516
NSN 6135-01-177-3552
NSN 6620-00-448-4378
NSN 6620-01-213-8772
NSN 5975-01-367-5392