This is the 3.5mm TRRS Female to 3.5mm TRRS Female Bulkhead Adapter. It features a 3.5mm TRRS Female connector on both sides. 3.5mm, also known as 1/8 inch, is an audio connector typically found on computers, laptops, smartphones, and tablets. Not to be confused with 2.5mm, which is a little smaller and far less common than 3.5mm connectors. Or 1/4" connectors, which are slightly larger and are typically found on high end headphones and music equipment. As a quick note for anyone who may not be familiar with TRRS connectors. There are three common types of audio signals: TS which stands for Tip and Sleeve. Which carries a mono signal. TRS which stands for Tip, Ring, Sleeve. Which carries a stereo signal. And TRRS which stands for Tip, Ring, Ring, Sleeve. This is typically used to carry a stereo signal with a mic channel. It can be mounted into a 1/2 inch hole and will allow you to create a pass through between a panel or faceplate, this is perfect for extending your run while keeping a professional appearance. The 3.5mm TRRS Female to 3.5mm TRRS Female Bulkhead Adapter is a quick and easy solution for your audio project. If you still have any questions, you can call our customer service department at 888-519-9505. For all your cable and connector needs, choose Show Me Cables.