Caution: I printed this myself, and it does need some tweeks !!

The hole for the pulley is a little too snug,
and the spacing for the pulling bolts needs to be widened, by 2 mm (or so)

All that said, it did appear to be very functional.

A pull tension, for my 3D Printer's 'Y' dolly,
using T2.5 Pully, and M5 Nuts & Bolts,

Print & build pully section:

Long M5 bolt, (shanked if possible)
Ball race , 11 OD, 5 ID
T2.5 Pully,
Second Ball Race,
Lock-nut,

test,
add washers,
cut off remaining threaded bolt,

Push M5 nuts in to holes,
drill two 5 to 6 mm holes, for bolts,
Tension belt,
Print away ...

This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/12Y8xVIN4fx