Speardiver C90 or C100 carbon fins?

I think C90, unless you are a pure freediver.

The C90 are the most recommended for all around hunting, as the C100 have some added length at the expense of agility when using odd finning angles, like say changing direction to PURSUE a fish.

I have the C90 medium stiffness in the HD pockets and think they are the cat's pajamas.

In Speardiver carbon fins the 90 and 100 designations refer to the total fin length (blade + foot pocket), from the front edge of the blade to the heel of the foot pocket. C90 fins are 90cm total length, C100 fins are 100cm total length. The length of the blade in C90 fins is 78cm, the length of the blade in C100 fins is 88cm. The length difference between C90 fins and C100 fins is 10cm.

It is true that the longer fins provide a little more propulsion, but at the expense of maneuverability. To offset the reduced maneuverability Speardiver C100 fins use a round cut for the front edge. The round cut offers a little less surface area, and no corners so less chance of the fin catching on structure.

I intended to market the Speardiver C100 fins for non-spearfishing freedivers, because theoretically they don't need to break form as much as we do when spearfishing. Think how we scramble on the bottom to look in a hole, or turn around fast to shoot a fish. Also in response to current market trends, because other manufacturers are offering the longer fins exclusively, and many divers are now convinced it's the only way to go without really understanding the longer fins.

This is how I explain the performance difference between the C90 and C100 fins. When you kick the blade pushes against the water and flexes, storing energy. Carbon wants to straighten out very fast and release this stored energy, resulting in your forward propulsion. It takes the longer fin (C100) more time to straighten/release its energy. So what you get is a slightly delayed action, the fin continues moving you for a little longer after you finish your kick, so you get more for your kick. I know it sounds appealing, but as with everything when you exaggerate one aspect of the fins performance you lose in another area. You can't subject C100 fins to your whim as you would with the C90, you can't accelerate as fast from a complete stop. The longer fins dictate your pace. Having stronger legs/kicking harder and faster doesn't really change anything here. You have to adjust yourself to the fin and let it do its work. The majority of divers who use the longer blades don't have the experience to understand the advantages and disadvantages, they simply bought into them. Still there are a few very experienced spearos who prefer the longer blades.

Obviously there's a limit to how long a fin can be while still being effective. If longer is always better then why not a 110cm fin, and then why not 120cm etc. You must conclude then that at a certain point the fin will become too long. Different people put that number in different places. The trend now in freediving fins is around 85cm for the blade, and I believe it's too long for me and %99 of freedive spearfishermen. Yet due to smart marketing the 85cm length blade is becoming the standard, and the 78cm blade is sometimes called "short". 90cm fins are not short! 10 years ago they were the original "long fins". I think 90cm total length (78cm bladed) is the ideal length for a spearfishing fin, and is what I and most guys use, you can't go wrong with it. But I acknowledge that divers who hunt in certain conditions and/or have a specific diving style, may benefit from using a 100cm fin.

The same logic applies to the fins angle BTW, the ideal angle being 25º. DiveR took the angle to an extreme 35º, with the end result of easier surface swimming but poor power return on an ascent.

I ahve the C90.

Difference is 10cm so 4 inches?

10cm = 3.94"

What's the difference between the round cut vs. standard cut for the 90 in length?

Are they both 90cm to the end of the rail (which would make round cut longer) or are they both 90cm to end of the fin?

Length to red arrow.

Zack, I have used the Speardiver C90 in about 15 surf entries without a problem and I really like the H Dessault foot pockets and Med stiffness blades. I just loaned Mike Morgan my fins to use at the island this week end. Hopefully he can also give a report when he returns. If I were still diving just Tahiti in deep blue the C100 would be a consideration. If I had money to burn and was a gear whore I would park a pair of C100 in the dive den just for the sexy looks alone. My C90 medium stiffness rock for my kick cycle.
Cheers, Don

Get the Speardiver fins everyone loves them and they have a warranty!

I have the Speardiver C100 and love them. I am waiting for some C120