This window operator is designed to be used with 1/2" diameter 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.  

Dimensions

• Overall Height: 2 3/16"
• Overall Width excluding stem: 1 3/16"
• Overall thickness excluding rotating hub: 1/2"
• Inside diameter of projecting torque bar hub: 1/2"
• Length of projecting torque bar hub: 3/4"
• Length of smooth section of crank stem: 1/2"
• Mounting hole locations c-c: 1 13/16"
• Mounting hole locations from flat edge: 1/4" from top, 1/8" from bottom