In an elongated medical device including a length of tubing defining an elongated passageway therethrough, said passageway having a surface of silicone rubber, and a rotatable metal insert extending the length of the passageway and bearing against the silicone rubber surface thereof for rotation therein, the silicone rubber surface having a friction with the rotatable metal insert, wherein the improvement Comprises a modified silicone rubber surface provided against the rotatable metal insert, said modified silicone rubber surface improved with respect to the slip characteristics Of the Silicone rubber surface against the rotatable metal insert by a reduction in the friction provided by a treatment of the silicone rubber surface comprising a plasma discharge which is provided inside the passageway.