If I buy a T7 handle-Do I absolutly need a rail adapter?
Or is there a way to attach it without one?
You need a rail adapter type seatpost as the T7 has rails.
Yup. Not rail adapter, no T7 bar.
No, not necessary.
I had mounted my T7 on a (KH type seat ) 4 bolt post. Had to trim about 2mm off one end of the post top to fit inside the T7. Also needed were longer seat bolts to reach thru all three pieces (seat base, T7, and seat post top).
Also a few washers between post top and the T7 on the front 2 post bolts will tilt it up nicely. Be sure to use nylon lock nuts on the bolts because they are difficult to tighten once the seat is mounted. (I always recommend those lock nuts)
It’s a little tedious cutting the post, dealing with the seat bolts, and adjusting the number of washers to get the correct seat angle, but once done, it works well.
Get a rail adapter if you can accept the extra ~1/2 inch height.
The T7 is a rail adaptor, and fits onto a bike-style seatpost. You don’t need a separate rail adaptor with it but it is usual to use the rails on the T7 itself. As Crashing has mounted out, that’s not strictly necessary if you’re prepared to do a bit of modding.
The rails are nice to have, since the tilt adjustment can improve comfort on long distances. The major benefit of the T7 is for distance riding, so this is a nice fit.
so to clarify any confusion, this is incorrect information. You need the following to make a seat work with a seatpost on a T7:
unicycle seat (normal 4 bolt seat)
T7 Handle
Rail type seat post