In contrast to the Zowie EC3-C, which has merely been shortened compared to the EC2, the Prime Mini has been sized down uniformly. As a result, it does feel quite a bit smaller than the regular Prime. Aside from the smaller size, the Prime Mini is no different from the Prime: The shape of the Prime Mini is commonly described as an EC2-type shape, which isn't wrong, but not quite right either. The best comparisons I can come up with are the ROCCAT Kain series and SteelSeries Rival 310. The Prime Mini has the narrow front and right-side back flare of the Rival 310, along with the flattish left-side profile of the Kain. The way the left side is significantly raised with a centered hump that slopes down gradually towards both ends is reminiscent of the EC2. The overall profile is bulkier than that of the EC2, somewhat similarly to the VAXEE Outset AX. Lastly, the back portion and how it integrates into the left side is not unlike that of the Rival 3 or Aerox 3. As you can see, design elements of all kinds went into the Prime Mini, forming a familiar yet somewhat unique shape. The main buttons feature fairly pronounced comfort grooves.
Much like on many previous SteelSeries mice, the sensor is shifted towards the back of the mouse. Though not as pronounced as on the Rival 3 or Aerox 3, the sensor still is positioned below the thumb level. Neither necessarily good or bad, this is, rather, just something that requires some getting used to.
As for grip styles, I'd say the Prime Mini is mostly suited for palm and claw grip. It is a medium to small mouse with a moderately pronounced hump, which should make it suit medium to small hands. For reference, my hands are 19 cm long and 10 cm wide, and I found the Prime Mini quite comfortable in claw grip.
Dimensions
This table includes the dimensions of the SteelSeries Prime Mini 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.
SteelSeries Prime Mini Dimensions
Prime Mini
DeathAdder V2 Mini
EC3-C
M4
Kone Pure Ultra
Base Length
11.5 cm
10.4 cm
11.4 cm
11.5 cm
11.0 cm
Length (including overhang)
12.01 cm
11.50 cm
11.92 cm
12.0 cm
11.7 cm
Front Height (lowest point)
1.1 cm
1.4 cm
0.9 cm
1.3 cm
0.9 cm
Height (highest point)
4.02 cm
3.84 cm
4.10 cm
3.91 cm
3.86 cm
Front Width (widest point)
5.69 cm
6.07 cm
6.13 cm
5.01 cm
5.43 cm
Back Width (widest point)
6.35 cm
6.25 cm
6.52 cm
6.68 cm
6.84 cm
Grip Width (narrowest point)
5.66 cm
5.52 cm
5.95 cm
5.86 cm
5.74 cm
Below are some comparison shots with each of the measured mice: