John A D
do these just snap on the various lenses and perform as wb filters?
Kind of. This one actually came with a 86nm WB cap and two adapters. Similar to other UV/CPL filters, you can screw it on the front of your lens or filter. However, I often got some difficulties to screw it on my UV filter so most time I just hold it.
Don't get chance to compare this with other high-end solutions. But I think in most case this WB cap performs the WB correction well.