You're not alone if you're wondering whether the preheat function is useful for your 3.5G CBD, HHC, THC vape pen. Empty 3.5ml Disposable CBD Vape Pen with Button Preheat & Adjustable Voltage Compatible with THC-B, THC-H, delta 11 THC, and delta 8 oils. Preheating your vape pen can improve the overall vaping experience and ensure that your oils are properly heated for optimal vaporization.