The IAG Timing Belt Kit is designed as a replacement for the OEM EJ20 and EJ25 engines. Included in the kit are IAG Adjustable Idler Pulleys, IAG's black racing timing belt, IAG timing belt guide, OEM idler, and timing belt tensioner. The IAG Adjustable Timing Idler kit is intended to properly align the camshafts on Subaru EJ20/EJ25 cylinder heads and/or blocks that were resurfaced (“Reducing” long block length), or utilize thicker head gaskets (“Increasing” long block length). The product is precision CNC machined and hand-assembled in-house. Each idler features a machined 10mm hex enabling your socket to hold it in place while you adjust the timing to perfection. The IAG Black Racing Timing Belt works with all Subaru EJ series engines. The belts are lightweight and utilize EPDM Rubber for increased durability and performance in all climates. The Kevlar construction is 300% stronger than the OEM belt and is also three times more heat resistant. The teeth are made of H-NBR grade rubber for additional strength. Extensive testing of this belt on our Spintron testing machine, as well as our fleet of racing vehicles, found that these belts ensure accurate timing and unmatched performance. The timing belt tensioner is one of the most important components in the Subaru timing system. Aftermarket, units are known to fail prematurely, which can cause catastrophic failure. The IAG Timing Belt Kit includes an OEM original equipment tensioner assembly direct from Fuji Heavy Industries. In Subarus, it is more common to experience a timing idler-bearing failure than it is to experience a failure of the timing belt itself. The IAG timing belt guide is the best method to prevent your EJ engine from skipping a beat. Each guide is machined from a single piece of 6061 billet aluminum and then anodized black for a protective finish. The guide is a strong, rigid replacement and adjustable to set the proper clearance for the timing belt.