This product is discontinued, please consider the upgraded Robot Gripper as an alternative product. This gripper is mainly made of acrylic board, driven by a small screw motor, which can provide a high clamping force. this gripper have two configurations, 4-finger configuration and 2-finger configuration, you can easily change the configuration to fit for special application case. Features: Marerial: Acrylic board Largest open size: 76mm Size Charts(mm): Useful Links Guide for Assembling the Makeblock Strong Robot Gripper Support If you have any further question for technical support, please contact waker@makeblock.cc or visit forum of Makeblock.