Hello, I purchased a pair from ACR EURO and for the money they have been good value. I wanted them as a matched pair so I could have two clamped to the milling machine at the same time. When I clamped them to a precision parallel 25mm by 30mm cross section I noticed one was low by .03mm. So took them to the club and skimmed the bases to the same size on the surface grinder. They are now spot on. No complaint with Arc Euro. I have seen the same quality at double or triple the price. Mine are the ones with just hole and no side clamping grooves. Made two alloy buttons so I could clamp via the centre hole/slot and not mark the ground slides. I bit of time on the milling machine and two clamps were made that hold down on the vice bed sides.
Good luck Phody
PS get the ones with the spring fitted to the jaw clamping bolt, if they suit your purpose.
PPS A 'T' handled 'hex' wrench makes tightening a pleasant operation.