FCS II CI Upright Large Thruster Surfboard Fins

The FCS II CI Upright Tri Fin Set – Large is a high-performance fin setup designed in collaboration with Channel Islands Surfboards. This fin excels in punchy, steep waves and is perfect for surfers who want rapid start-up speed, tight arc turns, and powerful performance in the pocket. With an upright template and a full outline, the CI Upright allows for aggressive direction changes while maintaining flow and drive.

Ideal for performance shortboards, hybrids, and step-downs with relaxed rocker profiles, this fin has quickly become a go-to for CI team riders who want less drag, quicker turns, and increased responsiveness—especially in critical sections of the wave.

This large-sized set is best suited for surfers in the 175–210 lb (80–95+ kg) range, offering enhanced control, power, and hold in bigger or more demanding conditions.

Key Features:

• Template: Upright shape for fast transitions and tight turning radius
• Performance: Instant drive and quick release off the top
• Ideal Conditions: Steep, hollow waves and beach breaks where tight control is key
• Fin Setup: FCS II Tri Fin – no screws required
• Construction: Performance Core for lightweight strength and speed
• Designed For: CI hybrid and high-performance models

Large Size Fin Specs:

• Fin Type: LRG Side / LRG Center
• Base: 4.50″ / 114.2 mm
• Depth: 4.70″ / 119.3 mm
• Area: 15.79 in² / 10190 mm²
• Sweep: 30.3°
• Foil: Flat

Fin Family – Reactor:

Speed. Snaps. Tight Turns. The CI Upright fits into the Reactor family, offering explosive performance, quick vertical maneuvers, and maximum reactivity in tight pockets and steeper faces.

The FCS II CI Upright Tri Fin Set – Large is built for surfers who demand speed, control, and precision under pressure. Whether you’re threading barrels or hitting vertical lips, this fin delivers the sharp response and drive you need to stay in control.

Why Shop at Rider Shack?

We’re a small, family-run surf shop dedicated to outfitting real surfers with quality gear. Every product we carry—like the CI Upright—is chosen for its performance, durability, and ability to elevate your session. When you shop Rider Shack, you’re supporting a shop that lives and breathes the surf lifestyle with curated gear you can trust.

Level up your board’s performance with the FCS II CI Upright Tri Fin Set – Large—crafted for power surfers chasing tight turns and responsive control.