Our Omura 180x is a fast cutting coarse stone that is best used on wide bevels like found on yanagibas, usubas, etc. This is one of my use in case of emergency stones that stays in my bucket at the ready. Great for working out low or uneven sections on wide bevels. Yes it wears fast but cuts fast too - keep it flat while working and you'll do OK with even the heaviest grinding.
Imanishi Omura 180x