From other stuff on Rectilinear IIIs in AK I'm assuming these are Jensen woofers. My set has the CTS which sit in front recessed and use 8 #10 philips head screws into wood. My tweeters and midrange have already been changed. I'm in process of evaluating woofers and crossovers now. They are now 3 way speakers. I've had mine since 1973.