I bought for RMRC1306 3300Kv for a hellbender 122.

Two have 1.5m hex heads and they work great.

Two have some weird smaller size. One of these came with a 1.25mm hex key. Only one of them.

I have a nice set of Wiha hex keys and the 1.5mm worked great on the 1.5m hex heads.

The weird size, the 1.3mm hex driver doesn't quite fix; it just spins on the service. But I have a few 1.25mm hex keys. I managed to get the screws in with these. But I can't get them back out. Now it just spins. It's kinda irking me. I have one motor falling intermittently and I haven't diagnosed whether it's the motor, ESC, or controller. I want to swap to motors but I can't easily remove two of them. If I get desparate, I'm going to have to cut a grove in them and use a screw drivers.

I read someone else online posting a similar complaint about screws with these motors.

I recommend you guys well at your friends in China that make all this stuff and have you send all the same screws next time and have them be standard like 1.5mm.