I picked up a box of 9mm Glow Ammo 255 rounds at Cabela's for $34.88 on sale, regular price is $49.99. These round self adhesive disks are placed on the back of the bullet BEFORE seating the bullet into the brass. This product is for someone that loads their own ammo. Instructions say that you can use these indoors and outside at sunset to sunrise. In making a batch of 10 to try at the indoor range I found the disks to be almost the exact size of the base of the bullet. It was hard to get it centered correctly. I was thinking that it could be pulled off center by the inside of the brass wall as it was being seated. No way to tell till you pulled the trigger. I went ahead and made up 10 to try, I even cleaned the base of the bullet before I applied the disk. As I'm doing this I'm thinking that will adding mass to the bullet change the internal pressure of the cartridge when firing? At the indoor range I was able to see or catch sight of the bullet going the 50 feet down range with just 3 of the bullets. I saw 3 more make it about half way then fly off into the wall or floor. The other 4 I did not see at all. Trying to catch sight of something going 1200 FPS within 50 feet is not easy. All you need to do is blink at the wrong time, so maybe I just didn't see them. I had a chance last night to try these outside on my daughters farm. I made some up, but this time I cut some of the disks in half and also into fourths. Out of 6 full disks we saw 3 travel maybe 100 feet, 2 flew off way to the right and 1 that did nothing. Next was the half disk, 2 that went 100 feet or more, 2 that did nothing and 2 that went into the ground within 10 feet. The next 6 were 1/4 of the disk and maybe not as bright we saw all 6 go well over 100 feet even tho we were aiming around 100 yards down range. I would NOT RECOMMEND this product. The video on Glow Ammo's website does not match what I got in the field.