2Pcs DM-S0020 2.1g Ultra-Micro Servo Coreless Motor 180 Degrees 2g Digital Servo with JR Connector 3.7V-5V for RC Hobby Model Airplane

not bad.

Buy something else. These are junk. I had a 3.7v system in micro airplane and one failed after just testing it with no control horn hooked up. So I replaced it with a different brand. The other one failed during first flight. I was lucky to retrieve aircraft with out a rudder. Complete junk from China.

Size was right, good torque. But after installation trial with no load, one servo produced a puff of smoke, and melted housing by the motor (pics). Other still functioning as expected. Will order replacement from different vendor, i.p.

Jittery and anemic. I was saved from their poor performance by them dying in less than 30 mins. I wanted to like them, but alas, that was not to be...