Looked in USEA rulebook and could not find this. A student of mine has a pair of reins with elastic inset just behind the buckle attaching the reins to the bit, has a leather piece "backing" it if you understand what I mean. It seems I read somewhere that if there is a leather back, i.e. the rein is all leather with the elastic inset "on top" of the leather that it is allowed. Does anyone know for certain, thanks!