Refrigerated FTL, the full truckload
Full truckload (FTL) reserves an entire reefer trailer for your goods. One temperature setpoint, no intermediate stops, no door openings en route, no handling by a third party.
That is what makes the difference on a temperature-sensitive product: every pickup or delivery stop opens the doors and lets ambient air in. On a load shared between several shippers, those openings add up and nobody can guarantee you the temperature range end to end. In full truckload, the trailer leaves pre-cooled, closes on your goods alone and reopens at destination.