I installed both the Glock Gen 3-4 Short Stroke Flat Trigger Drop-In Assembly and the Glock Trigger Spring Kit Gen 1-4. The M*CARBO video instructions were very easy to follow. I did all the polishing recommended, including the new drop-in assembly and the locking block. I opted for the max adjustment tool block for the flat trigger to reduce pre-travel. Pre-installation 5-pull trigger pull average was very good for a Glock @ 3lbs, even with only approx 1,000 rounds through it. Post-polish and installation trigger pull is only 2.2lbs - a 27% pull decrease! I highly recommend these 2 products!