Verified for patch 16.8.1

On Hit

Effect fires on each basic-attack hit (procs Guinsoo, Runaan's, etc.).

Also known as: on-hit, basic attack on-hit

What enables On Hit

Graves items (2)

Fragmentation Rounds On the Menu

Attacks send 2 fragments to nearby enemies on hit that deal 15% damage.
Fragmentation Rounds+ On the Menu

Attacks send 3 fragments to nearby enemies on hit that deal 20% damage.