A sliding valve for opening one or more fluid ports in a piping string, having a valve body and a sliding sleeve in a longitudinal bore thereof. The valve body has one or more fluid ports in an uphole portion thereof. The sliding sleeve is movable in the valve body between an uphole closed position closing the one or more fluid ports and a downhole open position opening the ports. The sliding sleeve has a longitudinal bore for receiving a collet, and/or a stop ring and/or a protective sleeve. The stop ring forms a stop shoulder for preventing downhole movement of the collet relative to the sliding sleeve.