Qosina 140322 Red Polypropylene Pinch Clamp, For 6.8mm OD Tubing (Pack of 25)

I've only used a few of these. Generally, they seem to work OK, but I've had one instance where one was used to pinch-off the clear plastic fuel line between the fuel tank and the carb of a lawn mower engine. Sometimes it appears that the clamp doesn't completely close the fuel line, allowing some seepage. This could be due to heat deformation of the plastic fuel line and/or of the plastic pinch clamp, causing a loss of pinch pressure. Or, perhaps the plastic simply deforms over time while under pressure. Not sure.