Tripack’s heat tunnel product line varies by opening (adjustable), overall tunnel length, and number of heating zones. Shrinking of film is a function of time and temperature. So, there is a correlation between tunnel length and conveyor speed based on product size and throughput. The HT-2 is our longest (5') dry heat tunnel and has multiple zones that can be set up independently. To achieve optimal shrink for a great looking product, it is common to use either a single tunnel or multiple tunnels.