Another take on a drive block for the extruder of the Zortrax/Wanhao D6/Monoprice Ultimate clonage for flexible filaments. Version 2 has a very tight fit for the 10.8mm diameter, 38 tooth Robotdigg Filament drive gear 4 flat shaft for nema17 stepper (RDGFDB) and the Micro-swiss lever for the Wanhao D6. The original D6 drive gear will also fit. The Robotdigg gear has wicked sharp teeth and thus much better retraction abilities compared to the D6 gear. No slipping anymore. You may have to sand the inner diameter a little. Clean up the print by drilling through the filament guide and smoothing the upper entry. I printed this in PETG but PLA or ABS will work just fine.