Fins

Top speed in a straight line, at the cost of turning.

Fins trade agility for straight-line speed. In practice the turning penalty felt small — one tester stacked them and said he was 'not really turning that slow'.

A 'dual fin' layout (two layers of fins) is common on hunters. Combine with Tiny Hairs or Quick Twitch if the turning bothers you.

Strengths

Very high top speed
Penalty is mild in practice

Weaknesses

Slower turns

Pairs well with

JetA propulsion jet that boosts your speed. Two jets on the back is a common pick.Tiny HairsCilia that improve turning. Small, cheap, easy to squeeze in.Leech MouthA sucker mouth that heals you while you feed. Slow killer, great at staying alive.

Used in these builds

Drill Omnivore — Drill kills, tube eats everything, shell keeps you alive while pushing.
Speed Hunter — Two jets, fins, jaws and horns up front. Catch anything smaller, outrun anything bigger.
Leech Tank — Tentacles hold targets, double Leech Mouth drains and heals. Wins long fights.

Where we saw it

Each chip opens the video at the moment this part shows up.