A catheter used to deliver a medical electrical lead to a right atrium of a heart in close proximity to a His bundle. An antioxidant is added to a mixture of materials before polymerization, or to a polymerization reaction mixture during polymerization or after polymerization. The adapter board has a first side including a first coupler. A width direction narrow groove 22 is provided The central narrow groove 21, the side narrow grooves 32 and the width direction narrow grooves 22 define plural polygonal block land portions 23 having five or more straight sides in the tread portion 10.