Here is a link and info for the sleeve and why we made it. We have since discovered that even with this sleeve the HR slave cannot handle the added load of aftermarket clutch kits and is why we came out with the HD CSC assy.
Zspeed HR OEM Slave Sleeve Info
Some people have had good luck with just the sleeve and a new OEM slave and others have still had a new slave die within 10,000 miles or less. The stock slave is just not that good.