even we have a battery in our b ody, we just don't know how long it will last eiter. Like laser battery, some go a long time, some don't. I jdon't have a lawer site on any of my gun but some years back I pu7t a set of the sites on my Smith model 342 and I shot the most amazing 50 shot group at 10 yards, I cold have ever dreamed about doin.