The 11D428A-16 (manufacturer's name RDMT-135M) is a liquid pressure-fed rocket engine burning N2O4/UDMH with an O/F of 1.85.
It is used for crew-rated spacecraft propulsion applications.
The previous version, the 11D428A (manufacturer's name RDMT-135) is still used as the reaction control system thrusters of the Zvezda ISS module.
The 11D428A-16 generates 129.16 N (29.04 lbf) of thrust with a chamber pressure of 0.88 MPa (128 psi) and achieves a specific impulse of 291 s (2.85 km/s).
This engine has been used with certain variations in the crewed Russian space program since the Salyut 6 in Soviet times.