The Greenough 4A is the most popular single fin ever made. The Power Blade is Greenough's latest design, developed over five years with Marc Andreini and Ellis Ericson. Both have Greenough's name on them. They're not interchangeable.
Here's when each one makes sense.
The Basic Difference
4A: Wide base, tapered tip, flex at the end. Designed for drive and versatility. Works from anywhere on the board.
Power Blade: Narrow base, stiff leg, wide "paddle" head that twists. Designed for speed and vertical surfing. Works from the tail.
Same designer. Completely different tools.
How They Work
The 4A
Water flows along the full base of the fin, generating lift and drive. When you push through a turn, the base holds while the tip flexes and releases. It's predictable, forgiving, and works whether you're surfing from the nose, the middle, or the tail.
This is why it works on everything from 10' logs to 7' eggs. The wide base engages whenever you put pressure on it, wherever you're standing.
The Power Blade
The narrow base creates almost no drag where the fin meets the board. Most of the fin's surface area is in the "paddle" head, which sits deeper in clean water below the turbulence.
The head doesn't just flex—it twists side to side, like a fish tail. Greenough calls this "variable tow." When you turn, the head twists into the turn, the tail steps out slightly, then snaps back as you straighten out. It generates drive through the twist, not through base pressure.
Marc Andreini's explanation: "You can run in flat out trim or pull the board straight up the face with the drive of a thruster during a hard turn."
The tradeoff: it only works when you're driving off the tail. There's no base to engage when you're standing forward.
The Right Board for Each
4A Works On:
- Longboards (9'+)
- Mid-lengths
- Eggs
- Vee-bottoms
- Hulls
- Pretty much any single fin box
Power Blade Works On:
- Edge boards (what it was designed for)
- Flat-rocker mid-lengths
- Boards you surf off the tail
- Speed shapes where trim is the priority
Power Blade Does NOT Work On:
- Hulls
- Traditional logs
- Anything you surf from the middle or nose
The forums are consistent on this. Swaylocks and Jamboards threads are full of people who bought a Power Blade for their hull and regretted it: "Very directional. Lacks drive from forward stance. Wants to be turned from the tail."
It's not that the Power Blade is bad—it's incredible on the right board. But "right board" is narrow.
The Feel
4A: Neutral. Disappears under your feet. Lets you feel the board, not the fin. Holds when you need it, releases when you want it. No surprises.
Power Blade: Active. You feel it working. Quick response, snappy transitions, lots of speed down the line. Can feel unstable if you're not used to it or not on the right board.
One Jamboards user on the Power Blade in a Liddle hull: "Pleasantly surprised. The tiny little base loosened the heck out of my board while that big paddle kept me oddly stable."
Another on a Mandala edge board: "Made a night and day difference on drops, bottom turns and overall turning."
The difference is the board, not the surfer.
Price
4A standard: ~$75
4A Volan: ~$115
Power Blade: ~$200
The Power Blade costs more because the construction is more complex—unidirectional cloth layup, specific flex patterns that require hand-tuning, made entirely in California.
If you're on an edge board or committed to the flat-rocker single fin path, $200 isn't crazy. If you're experimenting, start with the 4A.
The Call
Get the 4A if:
- You want one fin that works on all your single fin boards
- You're still figuring out your ideal setup
- You surf from different parts of the board depending on the wave
- You want reliable and proven
Get the Power Blade if:
- You're on an edge board or flat-rocker mid-length
- You want to push single fin performance toward thruster territory
- You surf mostly off the tail
- You've already dialed in your 4A and want something different
Don't buy the Power Blade hoping it'll make your log more maneuverable. It won't. Get the Volan 4A instead.
We stock both. Come by and we'll talk through what makes sense for your board.
For the full breakdown on all Greenough fins, see our Greenough Fin Guide.