After reconfiguring my K3 I have the following roofing filters for sale: 6 kHz $90 one available 1.8 kHz $90 two available 500 Hz $60 one available offset -0.75 Shipping is additional, and would be by Priority Mail Small Box where applicable (typically $6.80 in the U.S. if $50 insurance is considered sufficient) 73, Erik K7TV