it also slightly flairs them very slighlty allowing more room for wheel width and such i know as does a company down south call arch enemy who remove your arch liners then they underseal them allowing even more room im on 19s with arch liners in and they constantly touch im a mech with an arch roller ive rolled loads of cars from audis to mazdas mx5s to all sorts of random jap / vw slammed vehicles and if possible removing of the arch liners is always best u dont need to be on air ride at all