This is a coppertone finish left-handed, 13-1/2 in. single arm operator. It is made of heavy-duty diecast zinc with the baked on coppertone finish. The steel arm, worm drive and gears are protected with a corrosive resistant finish, and it opens to a full 90 degrees. The plastic roller on the end of the arm insure a smooth operation as it slides through the Prime-Line part TH 22397 track. When installing, the housing easily fastens down to the window sill.