I needed some additional clamps for a dresser I'm making.  I knew these clamps had a good reputation so I read the Amazon reviews and bought four of them.  These are great!  The screw mechanism is very smooth and easy to use.  My other clamps used 1/2" pipe.  I HIGHLY RECOMMEND these clamps that use 3/4" pipe.  The 1/2" pipe clamps can flex.  I did not see any flexing with these 3/4" clamps.  Sure they cost a couple of dollars more and the pipe will cost a dollar or two more, but it's worth it.  I would buy these again.