Thruster Fin Size Guide
How to Choose the Right Thruster Fin Size for Power, Speed & Control
If you get thruster fin size wrong, your board will never feel right — no matter how good the shape is.
Too small? It feels skatey and unpredictable.
Too large? It feels stiff, slow and hard to turn.
This is the complete thruster fin size guide for Australian surfers who want their board dialled properly — whether you're riding shortboards, step-ups, grovellers or hybrids.
What Is a Thruster Setup?
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A thruster is a three-fin configuration:
Two side fins (left & right)
One centre fin
Invented by Simon Anderson in 1980, the thruster became the most balanced, predictable and performance-driven fin system in surfing.
It delivers:
Control in powerful waves
Reliable rail-to-rail transitions
Hold under pressure
Predictable release
But none of that works properly if the fin size doesn’t match the surfer.
The Golden Rule of Thruster Fin Size
Fin size is matched to surfer weight first, board second.
That’s the rule most surfers ignore.
Your board size matters — but your body weight determines how much surface area you need to push against water.
Thruster Fin Size Chart (By Surfer Weight)
If you weigh under 55kg, you’ll generally suit an Extra Small (XS) thruster set. These fins are usually around 4.3 inches tall.
If you’re between 55–65kg, go with a Small (S) set. These are typically about 4.4 to 4.5 inches tall.
If you weigh 65–75kg, a Medium (M) thruster is the standard choice. Expect fins around 4.6 to 4.75 inches tall.
If you’re 75–90kg, you’ll usually need a Large (L) set. These are generally 4.8 to 5.0 inches tall.
If you’re over 90kg, look at Extra Large (XL) thrusters, which are typically 5.0 inches or bigger.
In short:
Your body weight determines the fin size first. The inch measurement refers to the height of the side fins, which directly affects hold and control.
This applies whether you're using:
FCS style dual tab
Futures single tab
Glass-on thrusters
Why Weight Determines Fin Size
Fins create resistance against water flow.
Heavier surfers:
Generate more force
Need more surface area
Require larger fins to prevent sliding
Lighter surfers:
Can overpower large fins
Need smaller templates to stay loose
Fin area = grip.
Fin size = leverage.
What Happens If Your Thruster Fins Are Too Small?
You’ll notice:
Tail slides unexpectedly
Loss of hold on bottom turns
Inconsistent drive
Instability in larger surf
This often happens when:
Surfers copy pro setups
Lightweight fins are used in solid surf
Groveller fins are used in punchy waves
What Happens If Your Thruster Fins Are Too Large?
You’ll feel:
Sluggish rail transitions
Harder top turns
Reduced release
“Stuck” feeling in small waves
This is common when:
Bigger wave fins are used in weak surf
Surfers oversize for “extra hold”
Boards are already wide through the tail
Board Type Adjustments
Weight gives you your base size.
Board type fine-tunes it.
High-Performance Shortboards
Stick to weight chart exactly.
Grovellers / Wide Tails
Consider dropping half a size smaller for looseness.
Step-Ups / Solid Waves
Consider going half a size larger for hold.
Hybrids
Match weight first. Adjust only if necessary.
Thruster Centre Fin Size — Should It Match?
Most thruster sets have a slightly smaller centre fin (approx 3–8% smaller area).
Why?
Reduces drag
Increases pivot
Keeps release clean
Never oversize the centre fin unless you're chasing maximum control in heavy waves.
Thruster Template vs Size (Important Difference)
Size = surface area.
Template = outline & rake.
Two fins can both be “Medium” but feel completely different.
Upright templates = tighter turning
Raked templates = more drive
Fuller tips = hold
Narrow tips = release
Size keeps you balanced.
Template tunes your style.
Australian Conditions & Thruster Size
Here’s how typical conditions affect sizing:
Weak Beach Breaks
Stay true to weight or drop slightly smaller.
Punchy Reef Waves
Stay true to weight.
Powerful Point Breaks
Consider slightly larger for hold.
Overhead / Solid Conditions
Increase size only if you’re losing grip.
Common Thruster Fin Size Mistakes
Copying pro surfer setups
Oversizing for confidence
Undersizing for looseness
Ignoring board tail width
Not adjusting for wave power
The majority of surfers perform best by staying within their weight category.
Eveley Thruster Size Recommendations
If you're riding Eveley thrusters:
4.5" Classic Thruster → Small surfers
4.7"–4.75" templates → Medium surfers
5.0" Big Boy Thruster → Large surfers
Match your weight first. Then tune template.
Quick Thruster Size Decision Formula
Check your weight.
Match to size chart.
Adjust only if:
Board is unusually wide or narrow
Waves are unusually powerful
You have advanced preference
If unsure — stay true to weight.
Thruster Fin Size FAQs
What size thruster fins should I use?
Use your body weight as the primary guide. Most adult male surfers fall into Medium or Large.
Can I use Large fins if I’m Medium weight?
You can, but expect reduced looseness and slower response.
Does fin height matter more than base?
Both matter. Height increases leverage. Base increases drive.
Should beginners use larger fins?
No. They should use the correct size for their weight. Oversizing can hinder progression.
Do bigger fins make you faster?
No. Correct sizing makes you faster. Oversizing increases drag.
Final Word
Thruster fin size is not about preference first.
It’s about physics first — preference second.
Get the size right and:
Your turns will feel connected
Your speed will carry through sections
Your board will respond predictably
Everything else — foil, rake, material — is tuning.
But size is foundation.