Naniwa 'Chosera' (Cho=Ultra, Sera=Ceramic) stones.
Designed to be a substitute for high quality natural stones in performance, these magnesia binder stones offer a very smooth feeling combined with rapid cutting speed in most steels and good dish resistance.
Highly regarded for their smoothness, high performance and generous size.
(Please note: These are the 'original' Chosera stones, not the newer export only Naniwa 'Professional' stones. To the best of our knowledge, the Professional are the same as the original Chosera but in a slightly smaller size and different packing.)
P.S; These stones are no longer being supplied without fixed bases and they will not be available again. Sorry.