These extension adapters are designed for engine oil pans with a recessed oil drain port in order to install the Fumoto Engine Oil Drain Valve without hitting the engine oil pan wall. Each adapter is roughly a 1/2" in length. ***ADL-106, ADL-109, and ADL-22 are an 1" in lenth. The adapter are compatible with the valves of the same 3 digit number (i.e ADP-106 matches with F-106, F106S, etc). *** ADP-22, ADL-22, ADP-116 and ADP-710 are special cases.