Rain Bird X43008 MDCFCAP Easy Fit Cap Adapter Black complete system of compression fittings and adapters for all tubing connection needs in a low-volume system. Faster and easier to install—requires up to 50% less force to install tubing, making your installation project faster and easier. Works with virtually any manufacturer's 1/2 in. tubing, where the outside diameter ranges from .630" to .669" (16mm to 17mm). The eight components of the Easy Fit System (3 Fittings and 5 Adapters) can be built into over 160 different configurations.