When sourcing a cart filler gun, prioritize heating precision and temperature stability, as most oils require a specific viscosity range (typically 60°C to 80°C) to flow without degrading. Ensure the device features a digital PID temperature controller and a heated reservoir made of borosilicate glass or food-grade stainless steel to prevent chemical leaching. For high-volume operations, look for adjustable shot sizes (e.g., 0.5ml to 5.0ml) with an accuracy tolerance of ±1% to minimize product waste.