PURPOSE: To ensure that an ink spreads well onto the surface of a type and printing with good dimensional stability can be maintained for a long period of time particularly for repeated depression of keys or printing, by incorporating a powder of a polytetrafluoroethylene resin into a rubber-like elastic member.

CONSTITUTION: A powder of a polytetrafluoroethylene resin is used as an essential constituent in an amount of 0.01W50pts.wt. per 100pts.wt. of a rubber form base material. If the amount is less than 0.01pts.wt., an effect on the dimensional stability in printing becomes poor. On the other hand, if the amount exceeds 50pts.wt., the viscosity of the resultant material is so high that it is made difficult to work or shape the material.