The inboard brakes used on JaguarÕs brilliant I.R.S. keep un-sprung weight to a minimum, but a tradeoff is poor cooling. For track- or high-performance street use, the rear brakes can easily overheat. Many solutions have been tried over the years but upgrading to vented rear rotors is one of the best. After poor availability from our previous vendor, we have now developed our own kits. Owners of Series I cars (with Dunlop calipers) can purchase the basic kit (17-1214) and source their own Girling calipers, or purchase this, 17-1620, kit which includes Girling calipers (lovingly rebuilt in our restoration shop using stainless steel pistons and all new seals), vented rotors, brake pads, rotor mount rings, caliper center spacers, caliper mount spacers, parking brake forks and lock tabs, stainless steel caliper cross over pipes plus all hardware. Finally, there were myriad differential castings; when fitting later calipers to an early differential, some clearance grinding may be required on the caliper mounts to fit them to the differential, but there is plenty of "meat" on the calipers to do this safely. In addition, some earlier IRS "Cage" sheet metal have a small opening that must be enlarged to accommodate the larger, later, calipers.