Far better than the tiny batteries - AimShot MBP223 Modular Battery Pack

This is a much needed improvment on the laser bore sight. However, I would like to have seen the cable between the battery pack and the head be a little longer. The battery pack has a small magnet, but when working with AR rifles, there isn't much metal to stick the magnet to.

While I found the tiny batteries had a very short life span, it was possible to close the bolt on the laser and hold it in place. With the wire coming out the back, this is not possible, so it can be difficult to keep the laser held tight in place.

But I will still take the extended life of the battery even if it isn't as convent as the self contained unit.