Cast steel fish tail pilot bit. Terex Texoma "TX Series" digger derrick pilot bit. This is what starts the auger into the ground and keeps it centered in the hole. This is the standard pilot bit that comes stock on (TXD) dirt and (TXC) carbide rock augers.
These work well on dirt augers but if drilling in rock step up to the (TX205C) with carbide tips. The carbide version helps not only cut drilling time but also increase the life of the fist tail.
See "More Photos" for auger bit diagram.
Similar to Pengo sb-25 part# 131740
