The material is silicon
NSN 5915-01-305-6516
NSN 5996-01-557-4160
NSN 6610-00-185-9434
NSN 6150-00-398-6527
NSN 5920-01-248-4498
NSN 6220-00-051-4198
NSN 5835-01-416-6455
NSN 5965-00-156-7372
NSN 6620-01-149-2842
NSN 5835-01-250-2939
NSN 5985-00-734-7479
NSN 6685-01-227-5134