This is the 3.5mm Mono Female to 2.5mm Mono Male Adapter. It features a 3.5mm Mono Female connector on one side. And a 2.5mm Mono Male connector on the other side. 3.5mm, also known as 1/8 inch, is an audio connector typically found computers, laptops, smartphones, and tablets. While 2.5mm is slightly smaller and far less common than 3.5mm. It can be found on older models of android phones or GPS equipment. The adapter will allow you to change connection types from a 3.5mm cable into a 2.5mm cable. The 3.5mm Mono Female to 2.5mm Mono Male Adapter is a quick and easy solution for your audio projects. 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.