Need help for Quanum Relentless Prop

[microboatdude]

I have a Hobby King Quanum Relentless that I'm running on 4s and 6s.

This boat here: http://www.hobbyking.com/hobbyking/s...dProduct=54640

The stock prop specs are this:

Specs:
Weight: 1.4g (per prop)
Dimensions: 39 x 13mm
Material: Nylon

I have no clue as what prop can work on this boat.