These are inserts inspired by https://www.instructables.com/Rain-Barrel-and-Diverter/ for a PVC 4-in x 2-in dia x Hub 45-Degree Combination Wye to turn it into a diverter for a water collection system.  The bottom portion resembling a cap and stand pipe is caulked into the bottom end (direction of the sweep) and the screen is inserted into the top end and held by gravity and pipes adapting your gutter to 4" PVC.

This is a parametric design which could easily be adapted to other materials and dimensions.  It is being used successfully to fill a 2 - IBC Tote water harvesting and storage system.