The material is silicon
NSN 6685-01-358-5314
NSN 7035-01-150-6303
NSN 5915-01-041-7941
NSN 5985-00-819-9334
NSN 5996-00-823-6081
NSN 5985-01-281-8483
NSN 5895-00-188-6798
NSN 5835-01-157-5886
NSN 5965-01-541-5801
NSN 6135-01-035-1871
NSN 6110-01-280-1296
NSN 2925-01-331-5039