The stock blades are 285mm. You can put longer ones on
but that just increases the load on the motor.

The blades that came with the MX 400 Pro have been
hallowed out and then covered in plastic. They are very
light....but very weak. Only good for low level hovering.

Heli-Max makes solid wooden blades for it that work
very well.

The original speed control comes preset for NO BRAKE
and slowly shuts down when voltage gets low.

The ESC will shut off power to the motor after 2 seconds of
no signal from the transmitter.

It will also shut down slowly if the temp exceeds 105 cenigrade.

A head speed of around 2100 rpm works well for new guys.

Hope that helps,

AB