Janser Green Box Concave Blades RWS007A. These concave blades are made in Germany for Janser of high quality steel boxed in 100s and sub divided in plastic dispensers which makes them popular with carpet fitters and floor layers because this keeps the concave blades safe in the tool box. These fit theJanser Coloured knives. they will also fit most standard pattern knives including all Dolphins and Dolphin style knives.