well i got some grips on it and tried to twist it but it snapped lol.
The bottom half of it that wasnt on the knurling part stayed in one piece though so ide reccomend cutting the top half of the plastic off, then sliding the bottom half down the stick. Cut off however much you want, then slide the plastic back up a bit. Put the black cap on so it goes onto the white part then refit the gaitor and knob.
Works perfectly for me i cut 1 inch off feels quite nice.