None of the connectors and tools are foolproof. Make sure to check the proper cut and flare of the outer conductor. Ideally, the connector should be disassembled after installation to check for the proper flare of the outer conductor. Also, remove ALL copper shavings from the foam dielectric. This is especially important in the 1900 MHz bands as a small shaving can create performance problems and high return loss. In addition, on the one-piece connectors that utilize the ball-bearing type of compression design, if possible, install these connectors only with the end of the coax you are connectorizing pointing up, or at least not down from horizontal. If installed with the coax pointing below horizontal it is very difficult for the ball-bearings to slide over the end of the coax and properly seat in the first groove. The connector will appear to be installed properly but the ball-bearings will not engage correctly and the connector wi ll easily spin and lose contact.