The ITTF approved S4 rubbers has a 2.0 mm sponge which helps you feel the ball and keep the control in your game. This blade has a concave handle with excellent comfort and grip. ROYAL FOUR STAR uses the Crystal Technology which is a specially developed blade treatment which increases the speed of the racket. Normal blade treatments use regular lacquer, but Crystal Technology employs a transparent hydrophilic gel lacquer specially developed by STIGA. Weight: 160 g.