I have a couple of MP31s and I love them. They were my first GMRS radios. Sound quality is better than I expected. Easy to use and quite durable. These are my go-to radios for anything short and simple like going up in the attic to work.
Used them on the beach once and talked for exactly 1 mile clear as a bell.
Up in the mountains in New Mexico they did fine. Every time my son disappeared around a finger out of sight, we still had coms.
Down at White Sands, the dunes were no problem.
Nice little gems these radios.