The Ocean key float is a miniature version of their round and cylindrical fenders, made in the same way and available in two colours.
These key floats are air-filled, so have more buoyancy than most other key floats.
Note that the round buoy key float has around twice the buoyancy of the cylinder fender, but is more bulky.
Dimensions
Round buoy: diameter 48mm / height 66mm
Cylinder fender: diameter 28mm / height 86mm
All dimensions quoted +/- 1mm