What size slow feeder should I get for a medium or large dog?

Across the reviewers we read, the rule of thumb is to match capacity to a normal meal: roughly 1.5 to 2 cups for small and medium breeds, and 3 to 4 cups for large breeds. r/puppy101 commenters specifically point large-breed and GSD owners toward the 4-cup Outward Hound, while r/pugs users recommend the smaller LE TAUCI ceramic for flat-faced breeds.