Replacement belt for the TD124 dimensions same as the original belt.
Tested with 16 other replacement belts and selected for minimal noise and correct tension between the motor pulley and step pulley .
Most replacement belts have way to much tension in excess of > 200gr/cm which give stress on the steppulley bearing and motor bearing.
Keep in mind that the belt stretch a bit over time and runs very quiet.
Cleaning the motor pulley and steppulley with alcohol once a year is recommended.