Optimum Performance and Durable Construction


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Your warranty begins from the date of purchase. Truefin has a limited lifetime warranty (excluding heel straps). In addition, the spines have a lifetime guarantee against breakage. Truefin has never broken a production injection molded glass filled nylon spine, and would like to obtain any spine that breaks for critical examination. If a user ever breaks a spine simply contact Truefin for a free replacement. The product warranty can be found in the owner's manual that is received upon purchase.

Contact Truefin if you feel you have a faulty fin or suspect a manufacturing defect.  Truefin will make things right!  The spines have a limited lifetime guarantee so if a spine breaks simply contact Truefin and arrange for a free replacement.  Truefin has not experienced any broken spines of all fins tested, so if a spine breaks, Truefin would like to study such a fracture and provide an engineering solution.  Computer Finite Element Analysis (FEA), as well as physical bench testing, has been conducted during the evolution of the exact spine geometry to maximize strength while using the least amount of material.  The result is a highly engineered spine which functions perfectly in this application.  Truefin was developed by engineers who are also divers in order to provide a kicking experience second to none.  The user should be assured that there is the absolute expectation that the spines should never break during use.

An Owner's Manual is provided with every pair of fins.  Also, the Owner's Manual may be downloaded at


Store fins flat to maintain quality - Avoid exposure to flame or excessive heat. Continuous and direct exposure to the hot sun is not a problem.


Buoyancy in salt water (including spines and excluding heel strap) - slightly negative (sinks) at 0.52 ounce (15 grams) per fin. Metal spring straps increase the negative buoyancy.

No, however if the user customizes Truefin, a right and left may be created.

Yes. Although Blue spines are great for all kicking styles, Truefin may be optimized for frog kicking without effecting flutter kicks after installing Green spines. A combination of a Blue spine used at the big toe and a Green spine used at the little toe improves canted frog kick performance (which creates a right and left fin). If a user wants the easiest kicking possible then Yellow spines are preferred, however the user will need to kick at a higher frequency for a given speed if Yellow spines are utilized. 

The color of the spine identifies the attack angle of the spine (and blade) and is established by unique vertebrae geometry of each different color. For example, when the vertebrae fits together like puzzle pieces which defines a joint, a predetermined amount rotation is provided. In the case of Blue spines, the joint between adjacent vertebra is allowed to rotate four degrees (4°) in a first direction, and twelve degrees (12°) in a second direction. If the spine (having five joints) is assembled with the teardrops facing up, then the blade will flex upward twenty degrees during the 'toe up' return stroke, and flex sixty degrees during the 'toe down' power stroke (four degrees times five joints equals twenty degrees 'toe up', and twelve degrees times five joints equals sixty degrees 'toe down'). Blue spines are considered best for popular use. Green spines have vertebra which causes the spine to be straight (0°) in the 'toe up' direction for enhanced frog kicks when pushing away with a flat blade, yet during the 'toe down' direction the twelve degree articulation between successive Green vertebrae will allow the blade to flex sixty degrees just like the Blue spines. Yellow spines limit the blade flex to be twenty degrees in the 'toe up' direction, and seventy five degrees in the 'toe down direction (15° x 5 = 75°). Yellow spines are for the easiest kicking experience, however a user will have to kick slightly faster for a given speed versus Blue or Green spines.

Yes, all sizes of Truefin Model 110 will accept the same spines.

We do not have a firm date as to when other sizes will be available, however work has begun on size Extra Large and size Medium.

Truefin has 13mm posts with 20mm flange, which is considered the 'large' post of common fin brands. For example, Truefin accepts fin straps made for Mares, Tusa, and ScubaPro brands.

Truefin first conducted subjective human flutter kicking tests in swim pools with very good results, however it was not possible to reliably and repeatably quantify thrust comparisons between different fin manufacturers. Truefin then built a test tank apparatus and equipped it with a motor driven artificial flutter kicking leg and measured the horsepower (corresponding to muscle exertion) with a rotary torque sensor measured at the output shaft of the motor, and measured the kicking thrust (pounds) with a load cell at the artificial 'hip joint' as a controller automatically kicked the fins from 1 to 100 kicks per minute while collecting data with SENSIT FUTEK software. Two different kicking range of motions were tested (27 inch and 36 inch 'swept tip') during all tests. Machine test results regarding thrust and efficiency of Truefin versus various categories of other fins are represented graphically at at COMPARISONS (PDF). Upon observation of the data it is apparent that Truefin provided up to twice the thrust (100% greater thrust) at specific kicking frequencies, and also Truefin had up to 65% better efficiency, depending on the brand tested. Relatively flexible fins of low quality were outside the scope of Truefin testing. Truefin has the comfort and easy kicking of highly flexible fins because Truefin readily forms an angle of attack which is enforced by rigid articulating spines, yet Truefin has measurably higher thrust then the stiffest technical fins. This results in an easy and highly efficient kicking experience when Truefin is kicked slowly, while also being a powerful fin when kicking rapidly. All tests were conducted, and all reports prepared, by an independent engineering consulting company.

All components of Truefin (except the heel strap) are molded, assembled, and packaged in the state of Washington, USA.