Well I hope all of your got as big a laugh out of this as I did. I never knew this: Only two normal sizes. Big and small. My local parts store had them laying on the floor and just handed one to me with a big grin. 
And thank you anyway John. For all the crap I’ve been faced with on my Jag recently, it is a happy moment to have something easy! Now to just get the cap to go down a bit so it’ll go in the groove.