If you've looked at our cage size guide (Cobra, Viper) as well as our cage specs page (Cobra, Viper), you may have noticed that the cage suggested for a given flaccid penis size is generally shorter than the flaccid penis itself. For example, the Cobra S has a total device length of 2.75" (7cm), but it is suggested for people who are 3-3.5" (7.5-9cm) when flaccid.
The short reason for this is that penises are squishy! When putting on your cage, it will naturally compress the penis by a certain percent. Not only is this normal behavior for the product, but it can actually be important for a good fit. This compression will help ensure that the penis fully fills the cage, with the head of the penis staying more towards the tip.