KLINGSPOR offers 6 sandpaper joint options for abrasive belts, which one should I choose? 
Recommendations are as follows. If you are thinking about going outside of these parameters, please check with our technical department first.

All portable belts #4 1st choice #3 2nd choice/ for glass belts

All Dynafile belts #4 only choice

Intermediate belts (includes backstand grinders and lever stroke sanders)
a. Cloth #4 1st choice #T 2nd choice after #4 failure/fine grits
b. Paper #4 1st choice #1 2nd choice for fine grits only Wide Belts

a. Cloth #4 1st choice #T 2nd choice for fine grits only
b. Paper #4 1st choice #1 2nd choice for fine grits only

All Pump Sleeves #1 only choice

Mold Sanders #6 first choice #5 2nd choice

Edge Sanding #4 1st choice #2 2nd choice, #5 3rd choice
**2nd choice for fine grits only designations are based on grits 150 and finer.