We have kits of two series HS and HSL
HS means Hydrox Systems and they are bigger as a size. Also, HS kits contain more liquid (Electrolyte) inside during operation.
HSL means Hydrox Systems Low cost, they are smaller in size and of course cheaper.
Any of this kit’s abbreviation means the engine displacement to which it can operate.
Both HS and HSL series operate at 12-14,5V DC. Do not forget to choose a PWM to control any of these kits.
Here you can choose Basic HHO kits (without PWM), HHO Kits with Constant Current PWM, and HHO kits with Dynamic PWM for Diesel or Petrol engines: