This ESC flashed with SimonK Firmware which is designed for Multicopters. The dimension of this 12A ESC is just about the same as 10A. Some sellers sell the same ESC under the name of 10A because not that many good 10A ESC available.
 
Description:
Item name: 12A ESC
Continuous current: 12A
BEC: 2A
Burst current: 16A (10 Seconds)
Battery: 2-3S Li-Po / 5-12S Ni-XX
NI-CD/NI-MH: 4-10 cells
Weight: 22g
Size: 32x22x5mm
 
Designed for: 
Multicopter with SimonK Firmware
Suitable SimonK Firmware is BS.HEX (you can upgrade it by yourself using KK Flash Tool)
 
Features:
Extremely low internal resistance.
Super smooth and accurate throttle linearity.
Safety thermal over-load protection.
Auto throttle shut down in signal lose situation.
Supports high RPM motors.
Power arming protection (prevents the motor from accidentally running when switched ON).
New Advanced programming software.
Package size: 20 * 10 * 2 cm / 8 * 4 * 0.8 in
Package weight: 67 g / 2.3 oz

Package list:
4 * Simonk Firmware 12A Brushless ESC Speed Controller