Well i have one...

the largest one for two horses and a llama.. yes its pricey but in my opinion worth every penny, it holds two bales of hay and they dont pull it all out cos i wedge it in so tight they can only get a mouthfull at a time,

you can easily move it when empty so avoids over poaching a particular area in the field, best thing i ever bought!!! and believe me ive tried many things over the years!!!