The JellHead has replaced parts of their hosts body with hardened but flexible Jell.
The JellSkin is made out of either Inner or Outer Jell and will also take the same mutations as the that Jell.
Applied: Neck, Breast, Body, Tail, Limbs
When applying Mutations to or 6-[Limbs], it can always be applied in pairs of two 6-[Limbs].
For example, you can apply JellSkin on both front paws with only one mutation instead of having to use two mutations!