Harvia WL590 20 Rs Pro/ls Pro Protective Sheath (side & Rear)Harvia WL590 20 Rs Pro ls Pro Protective Sheath (side & Rear) The Harvia WL590 protective sheath is designed and approved for wood heated Harvia wood burning heaters (Harvia Pro 20 LS RS). The protective sheath considerably reduces the safety distance to combustible materials in practice, this makes the wood burning heater fit in a smaller space. The protective sheath is attached to the wood burning heater and conforms to the shape of the wood burning