That depends on what model you buy. There's the constant on, and the momentary, both are seperate models. Of course there's also the White/Infared models as well, but those are 175 lumen white so I assume you're speaking of white light only.
The constant on White WML does have the capability to be momentarily turned on, along with constant on, strobe, high and low settings

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We have them in stock if you're interested

. Just about to make a listing here in a second...
**Edit** Disregard as I see you're asking about the 6V, apparently my reading skills without coffee are lacking today.