1) Double ignition pin, automatic electrical pulse ignition device.2) Over water pressure protection device.3) Water-gas interlock valve device4) Winter-summer switch option for gas saving5) Anti-freezing device.6) Free hand shower.7)Anti-dry combustion protection device.8) Flame failure safety device is optional.9) Large capacity range from 5L to 20L is optional. 10) ODS device is optional.11) 20-minute timer is optional.12) Zero water pressure start for all capacity is optional.13) White coated, metallic white / silver / golden color is optional.14)The faceplate shapes are optional.15) Liquid crystal display (LCD) is optional.16)The competitive price is optional according to material collocation.