Help quick! At the store, need help.

I'm in Germany and I'm at the store trying to figure out what wattage of thermo cable to get. I need it for my uth source since they don't sell the pads here or anything else. What wattage should I get?? 15 25 50 or 80????

If you have a thermostat then I would probably get the 50 or 80, I have no experience with this though. If you can return, then get the 25, 50 & 80.

I'd do something like that.