L-ring seal is to create an air seal where the tyre bead and rim bead seat are not completely compatible. Where you have an irregular butt weld in the knurled bead seat area.or where, during initial inflation, the bead seating is very difficult or when an air passage between the bead and the rim is identified. or where overloads and severe operating conditions cause the rim deformation (deflection) which can result in air leakage.