The aluminum crimp caps are made of high quality laquered aluminum. Available cap colors include silver, red, and green. Other crimp cap colors are available upon request. Standard septa types include: Low Bleed NT Silicone Septa, .040" (1 mm) thick. Available with single-faced or dual-faced PTFE. Standard Red/White Silicone Septa, .040" (1 mm) thick.