A lot of remote controller or flash trigger use 2.5mm or 3.5mm shutter connect cable.
I already had a 2.5mm cable for my camera,but I recently got a new device which use 3.5mm cable,Should I buy a new cable? 
No, nobody needs to waste money on different shutter connect cable.
This adapter can let your 2.5mm shutter connect cable work with 3.5mm jack device.