Hydroplast manufacture HDPE fitting. It can be used in both hot and cold water applications and has an operating temperature range of -20°F to +250°F. There are two types of fittings, one that is threaded on the inside and one that is externally threaded. Hydroplast also manufacture compression fitting. It is a small plastic device that can be installed to create an air-tight seal ****ween two pipes. The fitting has a threaded male end and female end, the male end screws onto the outside of one pipe while the female end screws into another pipe on the inside. This product can be used for many applications including plumbing, HVAC systems, and more.