From TSC, this one piece CNC Aluminium bracket attaches to your Tokyo Marui 5.1 / 4.3 to accent it with an extruded thumb rest for an improved grip.
The front type thumb rest sits in a more forward position to accommodate a longer thumb rest position. The rear type thumb rest is in a more rearward position to accommodate a shallower, shorter thumb position. This unit is also available in other colors.
The A and B types vary with the pattern of the grip surface. With the front type model, the A has a waffle pattern and the B with a spiral print. With the rear type model, the A has circular holes while the B has ovals.