I use Layne Labs, though in the past I used Perfect Prey. They were fine, but I prefer Layne. Their rodents always weigh within the range specified on their website; they've never been out of any size I needed; the rodents are immaculately clean and packed in freezer bags of sturdier material than plastic. Each one is individually flash frozen and they tuck tail and legs neatly under the animal, so you don't get 'rat bricks' to hack apart. and you can order in quantities as low as 10. They're also pretty fanatic about their 'humane handling policy', which I appreciate.