I understand powerplusparts doesn’t make this replacement trimmer head. The STA1500 rotates clockwise, the replacement rotates counter clockwise. The trimmer won’t feed line without changing the polarity of the power head.
The STA1500 has a 2 speed switch in the power head with very short wires. The poles are soldered so I cut the wires and soldered them in reverse. This works, but the soldered wires are stiff and hard to get in to the space provided. If I did it again I would try to unsolder from the post. The other issue is the line trim blade cannot be reversed, you have to sharpen the other side.