I am a photographer, and burn through a lot of batteries for my flash units. I moved to rechargeable batteries a few years ago, but always had a problem keeping track of what had been used and what was fresh. I've tried several systems before finding these battery caddies. I put them in correctly when they are fully charged, and put them in upside down when I've used them up. That way I can quickly find fresh batteries in my bag when I'm in a hurry, and I can keep sets together for recharging. I think they're a great product.