In a nutshell, O1 steel is easy to hone and a very fine edge is achieved relatively quickly. PM-V11 alloy blades that are easier to sharpen than A2 and hold an extremely durable cutting edge for up to twice as long as A2. What does this mean in practice? If you’re roughing something to size or planing abrasive exotics then PM-V11 is probably the better choice. However, for fine finishing or the pure pleasure of working with the very sharpest of tools, go for the O1 option. 3.2mm(1/8") thick, lapped blades, 31.75mm(1.1/4") wide.