I don't believe they'll wear out & leak, because when you tighten them down, they seal- like a normal bleeder. It's only when you loosen the thing that the check-ball & valve activates.
Everyone that's had them really likes them, and Hot Rod reviewed them a few times. What's the GM size again, 1.50? I forget
 I think it came to me- 12mm x 1.50? Is that right?
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html
---Think your car could be pic of the week? Visit http://www.f-body.net
[This message has been edited by TomP (edited November 29, 2000).]