The material is silicon
NSN 5915-00-353-0853
NSN 5975-01-058-3838
NSN 6110-01-084-7555
NSN 5910-00-954-1603
NSN 5905-01-123-9715
NSN 6220-01-511-5148
NSN 6685-00-136-3151
NSN 6685-00-413-6671
NSN 5965-01-368-9994
NSN 5985-01-215-2210
NSN 6150-01-358-8963
NSN 5996-01-220-3203