Press-type end connections eliminate the need for soldering, reducing labor and material costs and eliminating the fire hazard associated with the process. Press-to-connect connections are designed for installation onto ASTM B88 types K, L, and M hard-drawn copper tubing. Coiled (annealed) soft copper tubing is not recommended but can be used if the ends are made round. Fittings in nominal sizes 1/2 in to 4 in feature molded recess O-rings which, when un-pressed, create leak paths at multiple points during the pressure test, to identify an un-pressed joint quickly.