Toyota M10S female ribe socket for serpentine belt replacement.

On Toyota models listed below, the serpentine belt tensioner nut (other than being an unusual size) is extremley close to the chassis rail which makes it impossible to get a ratchet on the socket.
With this specially designed socket it has a hex end on the socket allowing you to fit a 17mm spanner on the end and successfully release the tensioner to replace the serpentine belt. 

Models: 
Corolla / Celica / RAV4 / MR2 / Allion / Allex / Avensis

Engines: 1.8L 1ZZFE / 2ZZGE