Actually there are 1) Standard/original/long and 2) Short.

From the article Release Bearing
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If you are fitting an original A12 flywheel with a 60-series transmission, it says you need a "short" combination:
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Mine measures 21mm. Part number is 50501-H7500. Just arrived today from dealer, part number on the bag. So that is pretty much the shorter part in the picture, but according to the wiki, the standard length. I believe the two lengths must be standard and long. All the info on the wiki points that way.. My 1200 had the standard 4 speed, 28mm clutch and the engine plate along with the shorter sleeve.

Which type do you have?

As far as I know there are only two:

* Standard length
* Short length

The standard length is what came in the original 1200s.

To further muddy these waters that seem to be a source of confusion to many it seems. The tech wiki section on release bearing carriers is very poorly written and has grave errors (no offense to the authors, I think they did the best they could with the info they had). On my brand new out of the bag 30501-H7500 (same as 30501-H1000 according to dealer), the measurements very closely match what is shown as a 30501-H5000 in a couple places on the wiki. The wiki mentions a standard and a short version. What I have is the standard, which should mean there is a long version, not a short version. There is also a 30501-H8670 on the wiki, even a picture with the part number on the bag, but searching dealer sites comes up empty on that number. Not NLA but nothing. I know someone here must have some parts in their stash they can measure. Sure like to get my coupe back on the road.

I'm in the middle of a 60A five speed swap into my 73 coupe. I have had it installed but I had to pull it out because the clutch would not disengage. I have what I believe is the standard clutch sleeve according to the wiki info. I need the longer one, but the wiki is very unclear on the part number I need. Near the bottom they list a standard and a short version. I have three standards, pn 30501-H7500 which superseded 30501-H1000. I ordered a new one from the dealer thinking it was the longer but nope. I don't want to just guess on this (again). I think I need 30501-H5000, but hope someone can confirm. Anyone have a long version laying around? Please help!