Actually the donuts I've got for my instruments look like the bands used to
castrate male cows and I assume that's what they were originally for. You
can but a big bundle (100's) for cheap. They're easy to use, but just watch
out where you put them ;)

Doug

"jcarlyle" wrote in message
oups.com...
Here's a leak testing article that I found helpful:
http://www.borgeltinstruments.com/Leaks.pdf
Sure, it's commercial, but it gives a nice detailed procedure for leak
testing.

Note paragraphs 3 and 4 near the front. Mike recommends using rubber
donuts to prevent leaks (I thinking these donuts are similar to the
grommets used for feeding power cables into metal boxes). He also
concurs with Doug that cable ties or twisted wire are not good for
pneumatic systems.

-John