How to adjust the size of bolt and nut from the plugin?

Hello! I'm an undergraduate student trying to learn mujoco. I'm trying to use UR5E with a gripper to screw a nut, only to find that the manipulator is small and the nut is super big. the bolt and nut are from the mujoco plugin, I tried a lot but I cannot change the size of the nut. Could you please tell me what can I do now? Thanks a lot!