The EzGrip Pen/Tool Grip has the same benefits as the EzGrip Pen.
The rubber grip provides the same comfort, the same light touch, the same control, and the same ergonomic injury prevention qualities.

The Grips are used in schools K-12 used by students and teachers, colleges, industry, microelectronics and medical environments. The referred to as rubber grips, pen grips, pencil grips and grippers can be attached to or can replace existing grips on any pen, pencil or pencil-like tool for ease of use. Example Pilot G2, or Zebra Sarasa pens. The rubber grips are used on dental picks used in industry, probes, scalpels, modeling type knives and small hobby tools. Also use the EzGrip grip whenever repetitive motions are required to gain more precise control over the instrument used, and when small implements must be used over long periods of time. We're part of school supplies in the US, UK, Europe to Australia and New Zealand.

EzGrip Pen/Tool pencil grips are made of a rubber composite that is hypoallergenic and can be cleaned and chemically sterilized. The EzGrips have low electrostatic discharge - ESD, and shedding properties. They are used in industries requiring clean-room and electronics atmospheres. It is suggested the product be tested for each type of application prior to use. The grips can be custom manufactured for industrial and medical applications. Materials may be changed, and form-fit to specific tools and for desirable properties such as vibration damping also. 
Friction Alert!
The grips are rubber. When slipped over other rubber or plastic materials the friction created makes this a difficult task. We suggest using a drop of water in the center hole to lessen the friction. The grip will go on smoother and expand to suit the needed width. The water will evaporate.  Do not use oils. Oil will not evaporate.
You can actually cut open the back of the grip with a scissors and wrap it around and over existing rubber grips or larger products such as markers.. That old devil Friction will keep it in place. And if it doesn't, chances are you're using too much pressure and hurting yourself