I didn't try one with my horses, but hay stretchers are rather popular at the rescue close by. I did buy Blue Seal one for them in past. My former BO fed soaked haystretcher to her 30+ yo toothless gelding 3 times/day to help with the weight (not sure about the brand though).
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."