Qest Compression fittings are designed to make connections with polybutylene and pex without requiring the special crimping tools needed for the insert style fittings.  These fittings work on a variety of pipe types, including Copper, Pex, Polybutylene, and CPVC.

Qest fittings are sized by the inside diameter (ID) of the tubing it fits, NOT the thread size.  We have listed the the Inside diameter (ID) and the outside diameter (OD) of the tubing to help you select the right size fitting:

Call Size 1/4" ID fits 3/8" OD tubing; equivalent to 1/2" Female pipe threads

Call Size 3/8" ID fits 1/2" OD tubing; equivalent to 1/2" Female pipe threads

Call Size 1/2" ID fits 5/8" OD tubing; equivalent to 3/4" Female pipe threads

Call Size 3/4" ID fits 7/8" OD tubing; equivalent to 1" Female pipe threads

Call Size 1" ID fits 1 1/8" OD tubing; equivalent to 1 1/4" Female pipe threads