Breaker bars are great for heavy duty wrenching, and are typically built to handle serious abuse. They are typically very simply designed and feature a 180° pivoting drive head at the end of a handle.
Proto ratchet adapters, which are available in 3/8″ (J5247), 1/2″ (J5447), and 3/4″ (J5647) sizes, are designed to fit onto the end of breaker bars to improve their versatility and also make it easier to access fasteners.
One side has a female square drive recess, the other has a male square drive end.
These ratchet adapters can also be attached to other accessories, such as T-handles, and other square drive accessories that might not have built-in ratcheting functionality.
Essentially, they turn non-ratcheting breaker bars and drive tools into ratcheting ones.
Buy Now: 3/8″ adapter, 1/2″ adapter, 3/4″ adapter, via Amazon
Amazon’s pricing on some sizes are great, but the 3/8″ adapter is currently grossly overpriced there. If that’s the size you want (which is the one I bought last month and am currently testing out), get it at Zoro for ~$36. Zoro and Amazon have matching prices for 1/2″ and 3/4″ adapters.