The material is silicon
NSN 6105-00-920-7754
NSN 5998-01-468-5460
NSN 5996-01-163-5455
NSN 6320-01-319-3584
NSN 5920-01-171-9139
NSN 6320-01-296-3181
NSN 5835-01-031-7265
NSN 5935-00-233-9491
NSN 6220-01-167-7859
NSN 6135-00-161-0746
NSN 6150-00-240-0873
NSN 5930-00-221-6067