Wound or spring bearings are the ancestors of toroidal roller bearings. Their special design permits to absorb and neutralize the thermal expansion caused by extremely high operating temperatures and to secure accurate seating on the shaft. There are two main types available: BR, with spring rings and solid cylindrical rollers; and B, with solid rings and spring cylindrical rollers. They are mainly used in the metals market (e.g. continuous casting strands), where temperatures and shocks are extremely high.