RV-1X Variable Thruster Block
The RV-1X Variable Thruster Block is a part found under the 'Command and Control' category in the VAB/SPH editor.
It is an RCS engine, which consumes monopropellant and responds to RCS control inputs. It attaches radially to spacecraft.
The block has a rectangular attachment point with 2-5 'horn' nozzles protruding from its sides, which exert the control forces. The RV-1X is significantly smaller than the RV-105 RCS Thruster Block, with only 1/10th of the thruster power and monopropellant consumption of its larger companion. Five variants of the part are available: angled 4-horn, orthogonal 5-horn, orthogonal 4-horn, orthogonal 3-horn, and orthogonal 2-horn.