The algebra b p R, p P 1Y I n f2g, consisting of all measurable sets in R whose characteristic function is a Fourier p-multiplier, forms an algebra of sets containing many interesting and non-trivial elements (e.g. all intervals and their finite unions, certain periodic sets, arbitrary countable unions of dyadic intervals, etc.). However, b p R fails to be a s-algebra. It has been shown by V. Lebedev and A. Olevskiõ Ï [4] that if E P b p R, then E must coincide a.e. with an open set, a remarkable topological constraint on E. In this note we show if 2`p`I , then there exists E P b p R which is not in b q R for any q b p.