Size One 6-18 pounds (we think it runs smaller, 6-15 pounds) Size Two 18-40 pounds (we think it runs smaller, more like 15 pounds to about 30 pounds) Size Three is also available here, but the next size up from size two is actually the Thirsties Diaper Cover size Large. More pictures The hook and loop version is here: Thirsties Duo Wrap Hook and Loop. An exposed PUL ("wipe clean") waterproof diaper cover in two sizes that adjust with your baby's growth. Adjustable rise snaps. For use over any style diaper. Made in USA. See this on a baby Karen's comments: These are not the same fit as the Thirsties sized Cover . The fit of the Duo is trimmer and the size runs differently. I don't want people assuming they are the same as the others but with rise snaps when they really do run differently - this one, the Duo, is narrower and trimmer. Size 1 works with Cloth-eez prefolds sizes Newbie through Small; size 2 works with Cloth-eez prefolds sizes Intermediate through Large. Workhorse size NB and Small for size 1 Duo Wrap, Workhorse size Medium and Large for size 2 Duo Wrap. I think the size change might come at 15 pounds not the 18 pounds recommended below (baby shapes vary of course, so weight recommendations are always a rough guess). Great over unpinned prefolds (pad folded and just laid in the wrap) A no-pinning delight! Also lovely over fastened prefolds or use over fitted diapers such as Workhorse diapers. 100% polyester with TPU laminate FREE of VOCs, PVC, phthalates, lead, and latex. Made in the USA. Also available in a lovely packaged set of 5 coordinated covers. If your toddler outgrows the size 2 cover, check out the Thirsties Cover in size Large. It has enough room inside to fit a very thirsty diaper. Thirsties Cover size large (not the Duo version) is the next size up from the Thirsties Duo Wrap size Two or the even bigger Duo Wrap Size Three instead. Thirsties Duo Wrap size Three is our largest cover. Fit tip - always put the extra fabric up when using rise snaps. Dino Rawr: See more pictures on babies. Size One has snaps in two rows across while Size Two has three rows of snaps across the front. This makes sense because of the width of the cover and it works wonderfully. There is no need for three rows across on the Size One cover and it's trimmer and less bulky this way.