I've designed this controller looking at a pair of Bushnell binoculars. The grips are vulcanized rubber over plastic and they open and close letting you adjust the piece for your hand size and finger lenght specs. 
Traditional controller design has grips that sit in your palms but little many players know; you mostly use your fingertips to stabilize the controller in your hand thus the short and small grips of a dualshock controller
