The description below is taken directly from the Stanley website. The ones I have are brand new still in the packaging. Any questions please feel free to reach out to me.

Half-round convex blade used for fast stock removal and shaping curved surfacesIdeal for work on fiberglass and removing filler (for cars and boats)Can be used as a replacement blade on 21-295 Surform® Flat File - Regular Cut Blade and 21-296 Surform® Plane Type - Regular Cut Blade