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.
Husqvarna spring retainer
Husqvarna nut, 3/8-16.
Carriage head bult
Lawn Tractor Nut
Screw hexagon head tapping srw
Washer thrust 5/8x1
Washer 13/32 x 13
Retaining Ring
Bolt hcs 5/16-18 x 1-1/2 in gr
Bolt hexagon head bolt 3/8-16