3.5mm Female Plug To 2.5mm Male Plug Adapter
This adapter has a mono 3.5mm female TS jack and a mono 2.5mm male TS plug. The connectors are gold plated to ensure a smooth, corrosion-free connection.
Note that this is a mono adapter. If you need this for a stereo audio application, such as listening to music on your smartphone with your standard headphones/earbuds, you should get the stereo version instead.