"These workbench clamps are handy enough and better than the pegs that you get with a workmate, but I have to say that the price is right for what they are but they are no substitute for a vice or grip clamp!
If you have lost your workmate issued pegs then get a set of these, but if you want to clamp and saw wood etc, buy a set of these: Irwin Quick-Grip 6" Mini One-Handed Bar Clamp - Product Code: 29139"
"I found the lock-down heads spring up, so you have to rely on tightening the nut tightly. They don't work in the outermost holes of my Black & Decker Workmates because the tightening nut fouls the Workmate mechanism, so they can only be used towards the center of the work top. The part of the clamp that is contact with the worktop dents the worktop. They are all plastic, even the thread, so I don't know how long they'll last with serious use.
I wish I'd just bought some G-clamps instead - more flexible, mark the underside rather than the top, metal rather than plastic"
"Bought this as i wanted some hold down clamps on bench , broke the first time i used it the alloy pin that holds the levers together broke in half. this pin as far as i can see is the weakest part on this clamp"
"They're cheap and that shows as soon as you start to use them. Being plastic you cant tighten much or they run over the threads. I'll save you some money by reading this, as I have a set and no practical use for them."