Here's the reply from Klipsch Product Support ... Part number/description: 1000595 - KD-16 (M) (NO STOCK) ,
" we no longer have stock of that item due to age of the product (as it has been discontinued and/or is no longer in production) "
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I think the KD-15-ST is an option to consider , previous forum members were impressed with this newer drone 's sound , it fits tight , and minor adjustments are needed to make it perfect with a dremel tool , it's a tad larger on the outer rim but not by much. the pictures are from a previous member's Chorus II installation of the Forte III drone .