I used FRM for a little while. The feed is usually full of crumbled dust, the rats didn't do all that great on it, and for the price, I could get Mazuri a couple dollars more, but MORE useful feed per bag, because it's not 1/4 dust in the bottom of the bag.

Check the ingredient list and percentages and compare to high quality foods and see if it's something you think you would like to use. Not everyone has access to the higher quality foods and FRM would definitely be better than things like dog food.