Need an extension longer than the “short” one and shorter than the “long” one? Snap-on’s new variable-length socket extensions might fill the bill. They’re also spring-loaded so they’ll stay on the fastener.
These look great for any kind of limited-access area down in an engine compartment, giving you not only the exact length of extension you need, but also providing a little pressure without you constantly pushing.
They’ll sell in two-piece sets with 4″ and a 7″ versions included for use with 3/8″ drive ratchets. The only bad news: they’ll run you a cool $90.
3/8″ Flexible Extension Set [Snap-on, Warning: PDF Link]