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-1 is our smallest (3') dry heat tunnel and has a single zone. To achieve optimal shrink for a great looking product, it is common to use either a single tunnel or multiple tunnels.