Due to the 90° angle and the large surface area, the enlarged bolt handle is easier to operate. There's plenty of space between the scope and the handle so you don't have to be worried about hitting the scope and cutting your hand.
When flipped down, the enlarged bolt handle has a low profile to make sure that you don't get tangled up when moving through the airsoft battlefield.
The entire bolthandle is machined from Aluminium. The knob's aggressive cuts not just look great but also make sure that you will not slip off the handle when you need to reload fast for the next follow up shot.
It's already included with the SSG10 A2 and can be bought for the SSG10 A1.