Available sizes and compatibility Open hole diameters: 53 mm, 70 mm, 85 mm, or 100 mm to match your speaker enclosure requirements exactly Designed for use with speakers and enclosures that require these open hole sizes, ensuring a precise fit Performance and design Reverse tube port design enhances bass performance for a deeper, more impactful low end The design helps optimize ported enclosure tuning to deliver clearer, more controllable bass response Durability and material ABS plastic construction provides durable, longterm use Built to resist damage during regular handling and installation Use scenarios Home audio upgrade: install in a bookshelf or compact floorstanding speaker to achieve stronger bass without adding external subwoofers DIY speaker projects: suitable for custom ported enclosures where precise port sizing improves overall sound balance Port replacement or refurbishment: worn or damaged port components in existing enclosures to restore bass performance Summary Multiple precise sizes for enclosure fit Reverse tube port design for enhanced bass ABS material for durable, longlasting use Clear benefits for enhanced lowend performance in various speaker applications