Accepts threaded filters with slide in/out drawer. Front end 2 1/4" wide which accepts SCT ring as shown. Four allen screws lock ring tight. Rear camera end has pentax threads. $105. for holder/drawer only. 1.25" slide in drawer available from AVA
Also for sale is a 48mm Schuler luminance filter with IR block, threaded. $50. Take both for $150. Paypal, MO, check when cleared.