Zipfit liners have cork and oil mixture in the heel and ankle area as well as on top of the tongue, when heated this mixture moulds providing great heel retention similar to that of a foam injected liner. The neoprene toe box ensures there is space in the forefoot. Zipfit liners also come with laces and a Velcro strap which aids the snug fit.
The main benefits of a Zipfit liner over a Foam Liner is it can be transferred to a different shell if you buy new boots. There is also the option of adding addition cork when the liner begins to pack out.