Hi group a VERY simple question for you ... (Hopefully)

I've got a Headlight which I use for fishing. It uses a
6Volt 4ah Sealed Lead Acid battery. My queation is
can replace the battery with a SLA of a 6v 4.2ah.
My limited understanding of this is that the "ah" is the
amount of charge it holds and for how long...and maybe it
has little effect of compatability as long as its a 6VOLT battery.

Is this correct ?


Cheers

Ian