I just replaced mine after dropping the bike 100 miles from nowhere and riding home with a fine mist spraying on my leg the whole way home. No damage to the bike other than the mystery of a cracked QD. It is definitely 5/16". I picked one up from coyote (http://www.coyote-gear.com/quickdisconnects.html
) as it was not too far off from me and shipping would be quick. Much better QD and great customer service as well. I also went ahead and replaced all the fuel line with HP fuel injection line rated to 250psi. Overkill I know but the $10.00 in hose is just insurance as far as I am concerned.