They've been playing in this for about 5 weeks now, since they were just at 4 months old. Miles was just slightly bigger than his brother Calvin, at the time. Calvin needed a small towel in the seat next to him and a book under him, for the first week or so. Miles was just big enough for the smallest setting. At the time the were just over 12lbs, if I remember correctly. Now, they are both over 14 lbs and it fits them great.
When we first set up the jumperoo, I thought there were a lot of toys that the babies were likely to not find interesting, at least not until they were months older. Some looked like they were just thrown in randomly. However, from the start, I was surprised at how interested the were in various attachments. For example, there's a funny looking, blue frog that hangs overhead. Miles spent 10 mins just staring up at the frog, fascinated, the first time in the jumper. Currently, the first thing they both go for is the odd looking, hard plastic butterfly, with crinkle sounding wings. They chew on this most of the time they are jumping.
Both boys have incredible balance and strength as a result of playing in this jumper.
This jumper is so amazing that it's inspired me to write my first ever Amazon product review.
Buy this immediately. If your kids are anything like mine, you will not regret it!
Assembly was easy and took less than 10 mins.