The object in the image is a Korda Zig Float, a specialized piece of terminal tackle designed for carp fishing with an adjustable zig rig. Unlike a traditional zig, which uses a fixed-length hook link, this system lets anglers present a buoyant bait at different depths in the water column.

The clever part is that you can change the fishing depth without recasting. After casting, the float can be allowed to rise to the surface and then pulled down gradually, with each foot of line adjusted representing roughly a foot of depth for the hook bait. This makes it particularly useful when carp are cruising or feeding away from the lakebed.
Korda says the Zig Float is precision blow-moulded and designed to be tangle-free, with a soft insert and QC swivel. The complete Zig Kit also includes an anti-tangle sleeve and lead boom, while the float comes in medium and large versions for different fishing situations.
So, while it might look like a small, unusual fishing float to someone unfamiliar with carp tackle, it serves a very specific purpose: helping anglers accurately target carp at different levels without repeatedly changing rigs. In deeper water, that flexibility can be a major advantage over conventional fixed zigs.