I've been looking for a decent Variable ND Filter for some time now and stumbled across this one from K&F.Having recently purchased a new backpack from the brand and being impressed with the quality, I thought I'd treat myself to this filter. After all it claims to not have the dreaded X that almost all Variable ND Filters have.On first impressions the filter was packaged very well in a hard branded card box. Inside was a plastic clamshell style case, housing the filter safely in a foam material.Getting my hands on the filter, I was amazed with the built quality and overall feel for the price! It feels well put together and durable.Having only briefly tried it on the Canon 80D paired with the EF-S 17-55mm f2.8, there is a small amount of vignetting at 17mm. However this disappears as you zoom in. (The small amount of vignetting can easily be removed in post)Thanks to hard stops at ND8 and ND128 the filter doesn't cause that dreaded X.Pros:- Excellent value for money- Great build quality and usability- Minimal vignetting and colour cast- Nano X glass offers clarity, scratch resistance and waterproofingCons- Case could be sturdier (a metal tin and an insert to hold the filter snug when in the case would have been better)As stated above, my only disappointment is the case. It will keep the filter safe, however the filter does just sit inside on top of a piece of foam allowing it to slide around.All in all another quality product from K&F! I'm certain it won't be my last purchase from this brand!