DarkAngel hit the nail on the head. Any M203 leaf sights are useless on an airsoft gun anyway and are merely there for show. With a real 203, you lob the grenade upwards to get it the distance it needs to go, hence the way the leaf sights work. In airsoft, the M203 is a glorified shotgun that you aim directly at your target with and shoot. 2 very different operating prinipals.
That being said, I'm sure this sight will be welcome, because for the most part, most airsoft 203 sights I've seen are pretty flimsy at best. A nice steel knockoff of the real steel version would be a welcome addition to anyone wanting that extra realistic look.
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