Adapter For On-Stage M20 Subwoofers In Black (Ssa21). The On-Stage SSA21 Subwoofer Adapter's female M20 threading attaches to M20 speaker shafts to accommodate virtually any subwoofer on the market, utilizing both removable M20 threading and a tapered, zinc-lugged lower section to accept 1 " cups. Whether it is a shallow M20, recessed M20, 1 3/8 cup or 1 3/8" cup with M20, the SSA21 will fit your subwoofer. Product Features Provides speaker shafts with M20 universal subwoofer adaptability 1 3/8" taper and removable M20 lug eliminates wobble and makes for a universal fit for all subwoofers on the market Solid steel construction item package weight: 1.0 pounds Shipping: Shipping is complimentary within the lower 48 US States. We Do Not Ship to PO/APO Boxes, HI or Alaska We Do Not Ship Outside of the Continental US All items ship within 24-72 hours of Payment For large items that require Freight shipping a valid phone number is required to call and schedule your delivery Terms of Sale and Feedback: Feedback is extremely important to us and If you are satisfied with our transaction, please take a moment to leave Positive Feedback. YOUR Satisfaction is our #1 Priority! If there are any issues, PLEASE contact us BEFORE leaving a neutral or negative rating so that we may resolve any concerns. We PROMISE we can make you happy if you give us a fair chance. Returns / Concerns: All items qualify for returns within 14 - 30 days of receipt. Buyer is responsible for return shipping on any item that is not damaged Please be sure this is an item you want before making your purchase. Customer Satisfaction is our TOP priority! All items are IN STOCK at time of listing. Inventory changes constantly and it is impossible to maintain a perfectly accurate count of all items. Please do not penalize us if we have to issue you a refund! Thank You For Your Business!