[R]

Rope Strand - A conductor composed of groups of twisted strands.

Round Conductor - a conductor whose cross section is substantially circular.

Rubber (Wire Insulation) - A general term used to describe wire insulations made of thermosetting elastomers, such as natural or synthetic rubbers, neoprene, Hypalon, butyl rubber, and others.

Rulan - DuPont's trade name for their flame-retardant polyethylene insulating material.

Rupture - in the breaking strength or tensile strength tests, the point at which the material physically comes apart, as opposed to elongation, yield strength, etc.