Hi there, you can see the lenght in the pics above (15,2cms) tube is ok for 1” steering (not for 1 1/8”).
But tube can be easily replaced if it too short for your bike.
Up for sale RS1 in very good conditions.
Last service was 3 years ago and only run 50/60kms at least.
It only needs to pump some air.
New Price: 200 € + shipping at cost
Thanks!