I know you have to be very carful buying from Harbor Freight and much of their stuff is pretty bad. I once had one of their quick squeeze clamps crumble in my hand the first time I used it so I threw the others out. However, I have to say I am very pleased with these hefty little clamps at an incredible price.
I have a few each of the short ones (maybe 6 and 10 inch) and they are working great.