Inserts come in loads of different shapes and sizes. I’m going to run you through some of the ones I have in my stash. They all effectively do the same job and the shape makes little to no difference on the performance.
For some inserts you can adjust the way you use them to get better performance, where this is the case I have added additional photos.
The most common of all inserts. This is just used as is. It will normally fit which nappy it came with extremely well, but you’ll find these a very universal fit for most nappies. Makes a great booster.
The vast majority of pocket nappies come with a standard rectangle inserts.
As the name suggests this insert is shaped like an hourglass. It gives a bit more width at the front and back, going narrower between the legs which can aid movement. This is also used as is. Some will have poppers if they are part of an Ai2 nappy.
Basically a very long rectangle. Will dry faster because you can unfold the layers a bit. Various folds are possible to place extra absorbency in your baby’s wet zone, potentially removing the need for further boosters.
The temptation is to just fold this insert in half. That will probably fit the length of the nappy nicely. This will give you two layers of absorbency. But by adjusting the fold slightly we can give an extra layer of absorbency, in the right place, improving the performance. I call this the Z-fold.
Like the snake but fans out at one end. Also benefits from the reduced drying time. Great for if your baby tends to wet the front or back of the nappy (boys, tummy sleepers, crawlers tend to wet the front. Newborns, especially girls, tend to wet the back). Can be Z-folded to place more absorbency in the middle if required.
A trifold is a flat piece of fabric, they are rectangular in shape but more square than a normal rectangle insert. Just like a prefold. These are designed to be folded into thirds to create that standard rectangle shape. The reason they are able to be unfolded is to speed up drying time. Rather than sandwiching several layers of fabric together these allow those layers to be separated. You can read more about trifolds here.
This is where you can get creative. Lots of brands offer flat inserts, but you can use any fabric you already have in this same way. Just fold to size, and you can place the absorbency where needed too. Normally the most affordable option (when you compare the materials/absorbency and price). Fastest drying.