HI-3129C Weiya / Makvision flyback transformer with single focus. We have tested this flyback in the monitor chassis in all three resolutions and also we tested this flyback to replace the HI-3129E dual focus and it works fine if your able to safely do the modification needed to install it in the dual focus applications. We have posted a picture to show the modification but if your skill and knowledge level aren’t high enough to successfully install this modification then please don’t buy this flyback for that purpose because if done incorrectly it could be dangerous to your health and safety and that of the monitor chassis. This flyback is found in the C3129 and M3129 monitor chassis. Modification Notes: leave the original wires in the socket and cut them a few inches long, then joined them together to the new flyback focus wire by twisting and soldering all three wires together, then heat shrink two layers with heat shrink tubing rated high enough for the voltage the wires carry, then cable tie them in place to the neck board. The fine focus on the sides of the dual focus application won’t have quite as much adjustment as the original but it was more than adequate when we did testing.