From ProTek RC:
The ProTek R/C Samurai RM Maifield Edition 3-Port .21 Competition Nitro Engine is Ryan Maifield’s weapon of choice when he steps onto the battlefield. The Maifield Edition combines features hand picked by ProTek R/C team driver Ryan Maifield, with the proven race winning performance of the ProTek Samurai platform.
The RM Maifield Edition features a unique backplate with steel insert to reduce friction. This helps to provide increased connecting rod lifespan, a more stable idle and higher RPM, while also eliminating the risk of aluminum debris in the engine due to backplate wear. The RM Edition is paired with the proven “high power” 21j carburetor and long stroke configuration, making it a great option for large track 1/8 nitro buggy and 1/8 nitro truck racing. A low CG 9 fin “RM” cooling head, 3 port sleeve and ceramic rear bearing round out the package to create a pro-level engine that delivers the power and performance needed to win, with the reliability required to compete at the highest levels of competition.