How to remove blur around mirror seam? I'm trying to mirror my object, but blur shows up around the seam, and it's only on one side of the object. How exactly can I prevent this from happening as it looks pretty bad when applying material. Here's the

Note: It's only when I shade the object smooth it appears. (Not sure if that's obvious, just wanted to mention it)
The Fix: If you don't need the non-uniform object-level scale for animation, CtrlA &gt; Apply the scale of your object.
Why that's a fix isn't obvious .. your object is scaled equally in X and Y, (though not  in Z). I would have thought normals would be transformed consistently.. it's strange that normals of adjacent faces which previously were equal, are not equal after after this scaling transform. I think we would have to dig into that calculation to figure it out.
The object has an Edge Split modifier with a threshold angle. You can sharpen the object all round by increasing the smoothing threshold in there. (The non-uniform scale makes the face-angles vary around the circumference, even though they all measure the same in object-space, so the effect progresses around the circle, rather than happening all at once)
Edge Split prevents normal interpolation across edges by duplicating them .. it's almost a legacy feature in this context. Probably better to use Auto Smooth, which splits the vertex-per-face normals, rather than the faces themselves. (You can increase the smoothing threshold angle in there, too, for a fix, but the right fix is to apply the scale, unless you need it the way it is.)