TS = Standard with long outlet
TK = Standard with short outlet
RTS = Reduced with long outlet
RTK = Reduced with short outlet
SMS tees T-pipes that fits to "SMS" tubes, these tube dimensions are included in ISO 2037 and EN 10357 Series D.
DIN tees T-pipes that fits to "DIN" tube dimensions included in EN 10357 Series A, (same as the old standard DIN 11850 2nd series).
The polished DIN bends internal surface finish is Ra<0.8 micron, (HSF3 finish).