Castor arrived in a black & white box, not much larger than the mouse itself. After removing the two seals, the packaging opened up like a book, revealing the peripheral nestled in cardboard mold. There are no accessories included, no replacement pads, or premium membership cards. Instead, Mionix added a lot of stickers, and a small Quick Start guide.
Mionix shares many of its design sensibilities with Naos and Avior. The fine touches are similar, same soft-touch rubber coating, same sleek curves, same subtle RGB lighting. The construction is lightweight (there are no weight customization options included) and feels sturdy in-hand.
In terms of layout, there are 7 buttons: unified left & right click, a rubberized scroll wheel, a single DPI toggle button behind it, and two thumb buttons (Back & Forward) to the left side.
A lot of work has been put in designing the ergonomics, that's obvious from Castor's design. The shape has very subtle edges that make it different than other "all-grip" type mice. The left side, coated in textured rubber has a slightly deep indentation for the thumb, with the Back & Forward buttons following the upper edge. They're easy to press and give a clear, satisfying click.
On the right side, two grooves for the ring and pinky finger shape the overall curvature of the mouse. These allow all five fingers to find their place. Since they're not really pronounced, even light clawgrippers should find the fit comfortable.
Despite it trying to cater to multiple grip-types, the print is wider than Logitech G502, but slimmer than Something like Strix Claw.
Two very large PTFE mouse feet are positioned at the front and back of the mouse. Mionix also takes into account the user taking Castor apart, and leaves clearance space for easy pad removal. No other info is listed here, just "It's all about the craftsmanship" right next to the centrally positioned sensor.
Tracking is similar on a multitude of surface. PMW3310 handles speed mats nicely, and keeps its mettle on rougher control pads like QCK Heavy.
Mionix has strapped a 2-meter long braided cable with ferrite choke close to the custom header with a Mionix specific strain relief, ending in a gold-plated USB 2.0 plug. Considering how everything else screams premium, I wouldn't expect any less out of it.