Thank you for viewing! ^_^ This is an inner baffle made of birch plywood. I also love audio and have used various inner baffles, but none of them satisfied me...(^^;; So, I started making my own. For those who want to improve sound quality cost-effectively! Definitely! I am confident that it is a quality that you will be satisfied with. Material: Birch plywood (15mm thick / Unpainted) Opening diameter: 128mm (for 16cm speakers) Included: M5 screws 30mm + special size washers Free shipping, instant purchase OK Detailed specifications and features are summarized in the photos, so please check them. I think even beginners can install it with confidence. If you have any questions or concerns, such as "Will it fit my car?", or if you would like to request a custom order, feel free to comment. Also, if you would like to add other options, please comment and I will create a dedicated listing for you. Thank you!