This is the Hobbywing XERUN Justock 3650 G2 Sensored Brushless Motor. Considering the 3650 series has been around for a while and has proven it's usefulness, Hobbywing introduces the second generation, the G2.
The biggest and most notable advancement with the G2 is the updated aluminum can design. The first 3650 series used a iron case that looked bland and featured few ventilation holes. The G2 now uses an aluminum milled can that has been purpose refined with improved looks, improved ventilation and improved heat dissipation.