Hole diameter 9.5cm / 3 3/4Outter plate diamter 10cm / 4 About Us:Established in 1992, The Sound Exchange is a local stereo, home theater, and music store in central New Jersey. We cater to music enthusiasts and audiophiles, and we love what we do. We design audio systems for all budgets, from entry-level to high-end. Come in for a demo of the latest speaker technology! Terms and Conditions:Sale subject to applicable sales tax.We accept all major Credit Cards via PayPal and PayPal payments.We do not ship to P.O Boxes. Signature is required. We Ship to PayPal verified address only.We offer local pickup. Bring a copy of your PayPal receipt and Photo ID when picking up merchandise at the store.Items are also for sale locally, so we reserve the right to cancel the sale and issue a refund if the item sells in the store before we can remove the eBay listing.Please contact us via eBay, if your order doesnt arrive within the dates provided at the time of purchase, before leaving feedback.Some NIB items have been opened to take pictures.We stand by our products. Please call our store for technical support before leaving feedback so we can resolve any issues, rather than leaving negative feedback. Contact Us:eMail us thru eBay using contact seller function. Store Hours:Monday thru Friday 11AM to 7PM ESTSaturday 11AM to 6PM ESTSunday 12noon to 5PM EST