HIGH QUALITY GOLD PLATED RCA JACK SET FITS HAFLER / DYNACO OTHERS .100% copper high purity gold plated RCA jack for superior connections. Maximum panel thickness is .250 inch. Insulated shoulder washer fits 3/8 inch knockout. Uninsulated, they will fit a 5/16 to 3/8 hole. Shoulder washers color coded red and black. Extra backing nut included. I use these when upgrading  the Hafler, Dynaco, and Phase Linear equipment. This is the best grade RCA connector I sell. As always, thanks for looking.