Sonnax 2nd Gear "Corvette" ratio servo kit 77701-04K provides increased apply area resulting in improved holding power for firmer 1-2 and 3-4 shifts in 4L60 (700-R4) and 4L60-E transmissions. The servo piston features D-rings in place of the OE seal rings for improved sealing during apply and release. This kit is compatible with Sonnax 4th Gear Super Hold dual servo kit 77767K. Upgrade used for high performance or heavy-duty towing applications Improved D-ring sealing configuration Contents Piston Piston D-Rings (2) Housing Housing O-Ring