This adapter is very handy for connecting your stereo headphones to a guitar effect device such as POD or V-AMP.
PROS: The angled adapter part sticks out about 15 millimeters before the 90 degree turn, so it can be used even with a device which has a recessed headphones output jack. Typically the round shaped guitar effect devices benefit from this, most of them can't utilize an angled adapter which turns 90 degrees right after the 6.35 mm jack part.
CONS: This adapter grabs your 3.5 mm headphone jack quite tightly, so it may require quite big force to unplug. Also inserting requires quite a bit of force, two hands may be needed. You shouldn't try to unplug your headphones by pulling from the cable with this adapter, you may damage the cable.
PROS: The headphones plug will not drop out accidentally from this adapter, the connection is tight and good. Also the mechanical structure is solid and foolproof.