|Rear axle retaining nut as used on many Ram / Quadzilla / Apache / Barossa 170 + 250cc quads.
These nuts are fitted in pairs and are situated next to the rear sprocket carrier.
They are usually VERY tight + are often damaged during removal.
outside measurement "across flats" = 50mm
inner bore diameter (thread) approx. 31.5mm
nut width = 14mm