Yep they go all up inside you, passed the sigmoid and into the large intestine proper. Training to open the sigmoid is interesting, takes you relaxing, listening to your body, and poppers help massively. You also need to learn how to deep clean, which is a bit of a challenge itself. However, when you do achieve all of that and have 3 feet of dildo all the way up you, my god it feels good. There's nerve clusters at different points in your large intestine that these things reach and it feels amazing to trigger them. They're not for everyone, but if you're into it, it's well worth trying.