This window operator is designed to be used with round torque bars. Torque bars are long horizontal bars that connect the left and right sides of windows to disburse the torque of cranking the operator across both sides of the window. Many 1960s and 1970s vintage trailer windows use torque bars. There are a number of different operators available so rely on the stated dimensions as well as overall shape to determine if this is the correct operator for your window. Some people call this a Phillips side mount operator, but we have not confirmed that it is used exclusively on Phillips windows.