B32B 3/20

Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form ; Layered products having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by an internal layer formed of separate pieces of material {which are juxtaposed side-by-side } of hollow pieces, e.g. tubes; of pieces with channels or cavities