This is to replace the 40 year old sun affected Venetian Blind Winder Knobs on my parents blinds. The centre hole is 3.5mm Diameter to suit the original steel wire winder arm.Printing: Infill 20% Layer Height 0.2mm Number of shells 2 Feedrate 90 mm/s Travel Feedrate 150 mm/s Print Temperature 230c This was printed with white 1.75mm PLA on mbot Rep2. Assembly: 1) Ream centre hole to suit wire winder arm or heat wire & push on new knob to enlarge hole. 2) Fix with in place with Cyanoacrylate or equivalent.