I found this Boat in resort Stará Turá – Dubník in west of Slovakia. Fences here was really narrative.
You could choose form three sizes:
size 51 ‒ circumference 51 mm ‒ diameter 16.2 mm
size 53 ‒ circumference 53 mm ‒ diameter 16.9 mm
size 55 ‒ circumference 55 mm ‒ diameter 17.5 mm