I have a couple of aplix BBOS. I like the fact that they come with a OS combo insert - MF on top of hemp works well for us. However, I found that this insert was way too bulky initially for DD - it made the legs really gape on her and we had to use alternative inserts. And I also found that they could leak BF poo. But now she's bigger they're a great fit on her.
Get a WeeNotions embroidered onesize instead, they're far prettier and so much better IMO. I didn't like the Blueberry Onesize at all but I don't really like applix fastening nappies. I do have a few side snapping Blueberries but still prefer my WeeNotions.
Don't like the OS they are way too bulky on my LO, but the SS are lovely and trim, I also found we got wing droop with OS as my LO is soo skinny!! The small still fit her now at nearly 7 months so not too bad IMO!!
Agree that WN are prettier. just wish that the OS fit Iris better - I've had to swap two popper WNOS nappies as the gape around her legs was large enough for a bus to fit through. That's the downside of poppers - less adjustable than aplix. But then, Iris can also undo aplix in a flash, so that's a problem too.