I have both of the 4-16 VT-Z scopes, one is SFP and one FFP. So far the FFP is working well and the glass is bright, but glass is not very sharp at all. It is usable all the way up to the full 16X and the comma shaped side-wheel is nice. In hind sight I should have gone to a higher model like the VT-2 or VT-T that have better reviews.
My SFP model had better glass and I really liked it when it worked, other than a very stiff side wheel. I should have sent it back for one with a proper working side wheel, but the glass was great so I hoped it would loosen up with a little break in time. I never got any better and at exactly 1 yr the side turret fell off in my hand. It turns out the whole turret is held in by three 2 mm screws with only 2 threads engaged on each. Now I basically have a $120 paper weight with great glass. I'm pretty handy and would re-install with new screws, but the turret was assembled with permanent loctite from the factory and can't be dis-assembled to get to the screws. It did default to 10 yds AO, so it's on my wife's low powered springer now.