5/8" ID (before shrink) black shrink tubing. 4 ft. piece. Made of polyolefin. Has 2 to 1 shrink ratio. Polyolefin is the standard-bearer in the shrink tubing market. It heats evenly, doesn't bubble or split, and is self-extinguishing. It also offers greater flexibility than PVC shrink tubing. This black version is also UV resistant.