S5M means the teeth type is S5M.
1125 means that the circumference of the timing belt is 1125mm, it means that the belt has 225 teeth.
The 15/20/25/35 means the width of the timing belt is 15mm/20mm/25mm/35mm.
Please mention these three key informations if you need other timing belt.
Please contact us if you have any questions.