Liners are new "skins" for your bathtub, shower pan, or walls. They are installed over your existing tub or shower; nothing is removed. Liners are made of heavy gauge acrylic. This is the same material that new, pre-fabricated bath and shower stalls are made of. So, if you were to demolish your bathroom and put in a new pre-fab unit, this is the same material that the pre-fab unit is made of. You can re-line just the bathtub or shower pan itself, or you can also add wall surrounds.