This is a transmission rebuild kit for the Rear Wheel Drive Mazda RX7 with the Rotary 1.1L Engine and the 4 Speed "MRX4R" Transmission for years 1979-80 This Super High Quality Kit is made by TRANSPARTS Part# BK137A This Transmission has an Aluminum Case and is Rear Loaded. This kit will work for the following Mazda applications with the 15mm wide Single Ball Front Countershaft Bearing: RX7 Rotary 1.1L 1979-80 B2000 4 Cyl 2.0L 1980-84 This kit includes all New Bearings, Seals, and Gaskets! So why not use what the professionals use!? IMPORTANT! PLEASE READ! It is important to note that the Front Countershaft Bearing can vary! This Rebuild Kit comes with the 15mm wide Single Ball Front Countershaft Bearing! If you need the 20.5mm wide Double Ball Front Countershaft Bearing, please see our other listing! Don't get caught with a kit of lesser Quality!