Do you have a device with a 3.5mm plug that won't fit into your other device with a 2.5mm jack, such as a pair of standard headphones and a new smartphone? If so, you need this adapter from Monoprice!
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.
Important: Although this adapter will physically connect a headset to a smartphone headset/microphone jack, this will not allow use of the microphone. This adapter has TS (Tip-Sleeve) connectors with two contact points, while a headphone/mic device requires TRRS (Tip-Ring-Ring-Sleeve) connectors with four contact points.