Lenz - Nostrali screw plugs are available in steel, aluminum, and stainless steel. Aluminum plugs can be ordred a decal affixed denoting function of the plug. The standard threads are (G) BSPP, (R) BSPT, and Metric threads. Please make sure if you are using BSPP or Metric threads to select the correct thread sealing washer for your application. SAE or NPT threads are available upon request if the quantities are large enough.