An improvement to silicone insulation for implantable medical electrical leads includes a plurality of ultra high molecular weight polyethylene multi-filament fibers, wherein each of the plurality includes approximately 25 monofilaments and has a titer of approximately 25. The plurality of fibers are embedded within a wall of the insulation that has a thickness of no greater than approximately 0.008 inch. A first fiber of the plurality preferably extends helically, and a second fiber of the plurality preferably extends linearly such that the second crosses over or under and directly adjacent to the first at a plurality of points, which are spaced apart from one another along an overall length of the silicone insulation. The aforementioned wall thickness is maintained, since, at least at each crossing point of the first and second multi-filament fibers, a coincident cross-section of each of the fibers is compressed in the radial direction.
