Micro Gearmotor Shaft D Shape

Hello the Micro Gearmotor Shaft D Shape,

Specs says it is 3 MM Diameter, but it does not indicate the Size of the D Cut,

But I need to know it’s D Cut sizing to design the appropriate fitting for it.

Can anyone Elaborate ?

https://www.sparkfun.com/products/12285

It’s not indicated in the datasheet https://cdn11.bigcommerce.com/s-tnsp6i3 … 92.png?c=2 - my guess is it’s either 2.5 or 2.75mm…but the best idea would be to get one and measure it