XHH to oznaczenie kabla wg NEC / UL (USA): X = Thermoset (cross-linked polyethylene) insulation; HH = High heat resistant, 90 C; XHH = Thermoset (XLPE) high heat-resistant building wire, dry and damp locations. 600 V, 90 C dry and damp. UL 44; NEC Article 310.