Feature: 1. Made of ABS plastic material, sturdy and durable, suitable for 6-10inch speaker. 2. Adopt exquisite workmanship, perfectly fit your speaker, reliable to use. 3. The inner wall is smooth, with both ends designed as horn mouth. Smooth airflow, obviously reducing the sound. 4. The speaker phase-inverting hole, also called sound tube or air hole, is often used in the inverted-phase speaker. 5. The inverter tube is mainly to pour the sound pressure of the airflow vibrating inside to the front, and overlap with the sound pressure radiated from the speaker to make a bass effect. Specification: @font-face{ font-family:"Times New Roman"; } @font-face{ font-family:"宋体"; } @font-face{ font-family:"Calibri"; } @font-face{ font-family:"Arial"; } @font-face{ font-family:"Tahoma"; } p.MsoNormal{ mso-style-name:正文; mso-style-parent:""; margin:0pt; margin-bottom:.0001pt; mso-pagination:none; text-align:justify; text-justify:inter-ideograph; font-family:Calibri; mso-fareast-font-family:宋体; mso-bidi-font-family:'Times New Roman'; font-size:10.5000pt; mso-font-kerning:1.0000pt; } span.msoIns{ mso-style-name:""; text-decoration:underline; text-underline:single; color:blue; } span.msoDel{ mso-style-name:""; text-decoration:line-through; color:red; } @page{mso-page-border-surround-header:no; mso-page-border-surround-footer:no;}@page Section0{ } div.Section0{page:Section0;}Item Type: Inverter TubeTotal Length: Approx. 102mm/4in (as shown)Hole Diameter of the Speaker Shell: Approx. 71mm/2.8in (as shown)Material: ABS plasticCompatibility: 60-10inches speaker Package List: 2 x Inverter Tubes