BudsGunShop.com - What is the difference?

First buds isn't using the correct photo for this tactical version. The tactical version looks like it has upgraded sights and a a2 style flash hider instead of the slanted muzzle. Other than that couldn't find much difference. Copy this model number and type it into Google for the correct photo RI4090N. Hope this helps.

Keith, this model has a receiver side rail for optics mounting, S7 Steel Bolt Carrier - S7 Steel Feed Ramp & S7 Steel Front Trunnion. The other model does not have an Optics Rail on the receiver. Stock level of both may be playing a part in the price difference. Cheers and stay safe!

The only difference i could find was the model
Model
RI4090N (the one you linked to) lists it as having a combloc side rail for mounting an optics rail, the other model (RI3291-N) doesn't list it as having the side rail.
And oddly enough the one without the side rail is listed on Century arms website, while the one with it is not listed on their site.
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centuryarms.com/vska-poly-7-62-x-39.html