Shape

The idea that the Castor Pro isn't your everyday, run-of-the-mill right-handed ergonomic shape is underlined by the fact that I really struggled to find anything similar to compare it to. When taking a closer look at the shape, the first thing that is noteworthy is how the width changes between base and top. Towards the front, the sides are slanted like this: \ /, creating a smaller footprint compared to the back, whereas the difference between base and top is less pronounced. In fact, the back flares out quite a bit, resulting in a wide butt somewhat reminiscent of the Sensei design. The right side even has a slight right finger rest, albeit not as large as that of the Naos. And while the centered hump is rather flat across its width, it slopes down to a significant degree towards the front and back, resulting in the front sitting lower than on many other right-handed ergonomic designs. The left side being barely raised further contributes to the impression that the Castor incorporates several design elements usually encountered on ambidextrous shapes. As a whole, the Castor is of an odd yet surprisingly comfortable shape.


As for grip styles, I'd say the Castor Pro is mostly suited for both palm and claw grip. It is a medium-sized yet somewhat wide mouse with a mildly pronounced hump, which should make it suit most hand sizes. For reference, my hands are 19 cm long and 10 cm wide, and I found the Castor Pro very comfortable in claw grip.

Dimensions

This table includes the dimensions of the Mionix Castor Pro and several other right-handed ergonomic mice. "Front height" denotes the distance between the base and main buttons. Measurements with two decimals have been taken with a caliper, while those with one decimal have been taken with a ruler. For a full list of all measurements taken, please refer to this sheet compiled by an esteemed community member.


Below are some comparison shots with each of the measured mice:


ROCCAT Kone Pro


Mionix Naos Pro