The material is silicon
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NSN 5925-01-561-7129
NSN 5996-01-604-3775
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NSN 6110-01-152-2831
NSN 4140-00-538-8959
NSN 5920-01-240-0219
NSN 5950-01-435-6354
NSN 6150-00-269-5017
NSN 6130-01-296-7302
NSN 5996-00-472-5387