Nut-Locking. The manufacturer has changed vendors and the part may vary in character. Some do not have a nylon insert, however the nut is a locking type.
Briggs & Stratton snowblower shear bolt kit. 1/4-20 x 1 3/4". Shear bolts are designed to break in half if the auger strikes a hard object to prevent damage to the transmission and engine. If the shear bolt is broken, the auger won’t be able to turn.