The original fork for the Riverside 120 petrol blue in size L. Compatible with the Riverside 100.
Steerer tube length: 214 mm
1 1/8"
For size M: cut it down to 194 mm
For size S: cut it down to 164 mm
For these two sizes, you'll then need to create a new thread. This can be a bit tricky, so don't hesitate to seek help from a proper bike mechanic if necessary