This is the Sirio S21 CL3B .21 1/8 Scale Off Road Buggy engine.

The CL3B was designed as a budget based engine for cost conscious racers, but the new CL3B has become one of the the hottest engines in the 1/8th Off-Road Buggy Class regardless of cost. The CL3B features a ABC construction piston and sleeve, a SG crank shaft, and a two needle composite carburetor. Get ready to tear up your local track with the new CL3B from Sirio.

This is aimed at racers wanting to upgrade from their standard engines that come supplied with their RTR car. Sold in a set it will come with pipe set and adjustable clutch system.