depends on your group if they're worth the money or not. My teen ds's it's definately worth the money! They're old enough to come and go without an adult and can also take the younger ones for me. I think they set a record last trip for the number of refills in one night lol. I think they're about $12, vrs refills that are $2,50-$3.00 each. We get our money's worth in one night lol. They are plastic and they do come with lids, but the lids are not spill proof. They have an opening in them, so a toddler will dump them if he turns them upside down. I think they're 8 ounces, but I'm not sure and we've never measured. They used to be different designs for each resort, now I think they're all the same. We're going with ds16, ds15, 2 dd's9, dd5, and ds2, and will be getting the mugs for everyone but ds2. He'll get a sippy type cup and can share my mug when he fusses. My mother, sister, and neice are also going, and dmom will either steal mine like she did last trip or buy her own lol.