If you use our own Bountiful Baby bodies, you probably don't need any more of these, because we provide all the ties you need with the bodies. However, if you use your own bodies, or somebody elses, you may need these. The specific way to use them with other bodies depends on the bodies, but in general, they are used to secure the limbs and head to the body.
The 14 inch and 8 inch ties are super narrow-- only 2.5mm wide! Such narrow ties are normally hard to find, but they are what you need for most body applications in order to adequately hide the ties within the body.
If you are in doubt whether you need the 8 inch or 14 inch ties, then buy the 14 inch because you can cut them down to any smaller size you need.
The 11 inch ties are wider (3.7mm), for those situations where you need wider ties.