Be wary of the cheaper tunnels that have the green cover with the woven reinforcement. I found they tend to cause plants to bolt. I recovered mine after a couple of years in a commercial style clear ( well, very mildly green coloured) polythene and the difference was instant and amazing.
Also, make sure you have good ventilation as they get very humid which can cause you problems. I put a mesh covered ‘window’ at either end when I recovered the tunnel and again, the difference was tremendous.