Forgive me for my ignorance but I find this a great time to attempt to test what little knowledge I have.

I think they are for automatic trannies. After you hit a particular RPM it throws the tranny into the next gear. Like I have hear of people haveing 3500RPM stall converter or a 4000RPM stall converter.

Atleast I think that is right.... I'm probably wrong! I'll go sulk in a corner now.