It works but is not ergonomic and very awkward to adjust for two reasons. Small knurled screw. The part that compresses the tube is smooth and rounded, so the tube won't stay in place when the screw is compressed. I highly recommend the following clamp, just bought one to try - expensive but fantastic and very easy to control flow up to dripping at the rate of one drop every few seconds etc! Grafco Hoffman Flex Tubing Screw Compressor Clamp, Open Style, 1 x 7/8", 3083DZ (pack of 12) I've tried and the best, expensive but worth it. I found the second option a lot cheaper but I found them. Haven't tried them, but definitely way better than the ones reviewed here. This is a HUMBOLDT H-8722 "Easy Grip" screw compressor clamp, open jaw, 0-5/8" max height, 1" " maximum width.