These fittings are best used on 3/4" vacuum clamping jigs. With 1/8" NPT threads, the hole is small enough to easily attach to the center of clamping jigs. Item is used with 1/4" ID vacuum tube.
Review by Dave Finn
I have used these on a couple of vacuum clamps. They work great! I can only find the larger ones at Lowe's, but they deform my 3/4" plastic since they're 1/4" npt. I'll be ordering more of these from Joe!