These are a CNC molded 10” wheel side mount adapter with a 10.7” OD, 9” ID 5*, and a ½” mounting surface tilt to follow the flow more of the outside of the saddle bag, to allow a deeper speaker to be mounted with enough room for proper ventilation. Max mounting depth will vary by bag manufacture.
Fitment will also vary by bag manufacture. Using a Quality bag or stock bag will achieve the best results. The inside diameter may have to be opened slightly as there are different speaker manufactures on the market.