Fitting connections for corrugated metal tubing. The connection includes a body having an externally-threaded end, a nut or other fastener which is threadably engageable with the body end, and a collet which is receivable coaxially within the fastener. The collet is formed as a series of individual, arcuate tangs which are joined together by a retaining collar, the collar allowing the segments to be resiliently opened within the fastener so as to allow the crests of the tubing to pass therethrough. The fitting may be pre-assembled with the collet segments being received coaxially within the fastener with the collar extending rearwardly from the fastener, and with the fastener then being partially threaded onto the fitting body.