You might wish to read this alongside my post on gussets. There are a few different options for the style of leg elastics on nappies. Effectively they are all the same, so don’t worry about which one to get. This is more a quick breakdown in case you’re wondering what other cloth users are talking about.
The most common. These will feature on most nappies. Normal offer decent containment and are hopefully gentle on little legs. Some will also feature an internal double gusset, again see my gussets page for more on that.
A personal favourite of mine. Normally much gentler on the legs, so less sock marks. Can often mean you just need to double-check the legs to ensure the elastic has rolled inwards and nothing is sticking out.
This is one I’ve recently discovered. I’d call it something of a hybrid of the above two. From the small sample which I have used, the elastics are very gentle like the rolled elastics. They roll in when worn, but don’t require the same due diligence of checking that everything has rolled in correctly.
This is basically the same as the standard elastics but with an extra frill of fabric on the outside. Tend to be more common on wraps than nappies, although there are a good number of nappies with external double gussets if you like that design. I personally don’t really love this feature, and I’ve covered in it more detail on the gussets page, but here’s a few photos so you know what you’re looking for.