Swing circle of KAMAZ trailer, Zaporizhia region.

Trailer swivel circle (10 отв x 12 отв) 
The turning wheel is connected to thetrailer with special steel bolts. The turning wheel of the Kamaz trailer is equipped with fasteners for a stronger installation. All nuts and bolts undergo long-term heat treatment. The bolts also have cone-shaped surfaces for improved grip. Therefore, the turning wheel of the Kamaz trailer reliably protects the car from loads.(//tractor-service.com)
 
The Kamaz turning circle consists of rings (lower and upper) of a shaped profile. The clutch mechanism is very simple. The turning wheel of the Kamaz trailer, or rather its rings, are closed after filling with 112 layers of 25.4 mm diameter. The spare parts of the Kamaz coupling device, as well as the turning wheel, are important when attaching a trailer with atruck car.