These are the same cam gears we have been shipping in our UCON-EMS kits for many years.
They replace the stock exhaust cam gears found on the original single VVTi 1GR-FE 4.0L engine found in the 03-09 4Runner, 05-15 Tacoma, 07-09 FJ Cruiser, and the 05-09 Tundra as well as many other vehicles found in foreign markets.
The URD Cam Gears modifies the timing of the exhaust cam to allow for better cylinder emptying on the exhaust stroke, which in turn allows for better cylinder filling on the intake stroke with less hot end gas hanging around to heat up the incoming cylinder charge. This allows for great flow through the engine and allows for more aggressive spark timing.
The URD Cam Gears work great for Normally Aspirated and Supercharged applications. Not recommended for Turbos or other applications causing high exhaust pressure. Not recommended for aftermarket camshafts.
The URD Cam Gears are made in the USA by an aerospace company specializing in precision gears for aircraft and spacecraft and are properly ground and heat-treated for trouble-free service in your engine.