A coupler for a refrigeration system easily snaps and locks in position over a service port and securely seals the coupler with respect thereto. A tubular outer body includes a first set of cavities which captures a first set of rotatable spherical balls A tubular inner body is located within the outer body and includes a second set of cavities for capturing second set of rotatable, spherical balls. The inner body includes a recess therein for selectively receiving the first set of balls from said outer body. The inner surface of the inner body defines an interior which includes a spring-loaded plunger. When the coupler is placed over a service port, the barrel of the service port enters the interior of the inner body and the plunger means contacts a spring-loaded ball valve causing it to open. At the same time, the first set of balls drops into a recess in the service port and the inner body moves forward with the service port against the biasing of an inner body spring. Further forward movement of the inner body causes the first set of balls in the outer body to drop into the recess in the outer surface of the inner body.