This is a set of four filters, three of which are 52mm: an 80a blue; a Y(K2) Yellow; and a NX2 Neutral Density. The fourth is a Meade 4000 series Moon filter (1.25"). The 52mm's are Hoya brand filters, the best out there. The filters are in perfect condition, with no scratches. Included in this set is my 52mm to 48mm adapter ring. I have the cases for each. Yes, 2" eyepieces take 48 mm. I bought the 52mm on purpose.
Here's what (and why) I did: Spot superglue the 52/48mm adapter ring inside the bottom of your 2" focuser, then screw the filter in UNDER the focuser. You don't EVER have to change filters when you change your eyepieces (Big Barlows are NOT affected by this). I've purchased a Denkmeier Two binoviewer, which extends beyond the bottom of my focuser shaft, so I can't use this setup anymore. However, if I hadn't purchased it, I'd have kept this in my scope. I learned this trick from a fellow astronomer. I'll sell all four filters and the adapter ring for $30.00, including shipping via Paypal. Thanks for looking, and clear skies!