I've been using the Max-gain Systems cam-lock telescoping masts for well over a decade. Not cheap. And the ones I bought I had to glue the cams onto, which you do have to be careful with if you want the fiberglass tubes to extend/retract properly afterwards. But they are great for wires or verticals or 450/700/800 yagis, depending upon how far you want to raise them up and whether or not you actually use any guy rope/wire. At one location I had one of their 48 footers extended all the way, with a Alpha Delta 160m trapped dipole. I never used any guy rope, depending solely upon the inverted V wire at 48 ft to act as the sole guy. Granted, that only handled guying in two directions, but with the lightness of the load I had on it I never had problems. At another location I used to extend them up to 35' without any guying with a Diamond X500 (or was that 300) and a 700/800 yagi on it. Worked fine, and I could easily bring it all down. Of course, it's easier with 6-foot fiberglass lengths than 8-foot fiberglass lengths since one can then reach the bottom cam easily from the ground.
Not for everyone, or every scenario, but they have always worked great for me.
Mike