Bio-Fin XT Stealth (Black Stainless Steel Spring Straps)

The Apollo Bio-Fin XT Stealth is a high-hardness variant of the Bio-Fin Pro platform, engineered for operators requiring increased instantaneous thrust and stronger kick feedback. While maintaining the hydrodynamic split-fin architecture of the standard Bio-Fin Pro, the XT version utilises a compound approximately 15% harder than the standard model.

This enhanced compound increases resistance during the kick cycle, improving immediate force transfer to the water and delivering a firmer propulsion response. The XT configuration is recommended for divers transitioning from conventional paddle fins or for operations requiring swimming in swift currents or high-flow environments.

Although overall propulsive efficiency relative to total input power is marginally lower than the standard Bio-Fin Pro, the difference is minimal. The XT remains a high efficiency fin operating on a different performance dimension compared to traditional paddle fins.

Features

• Split-fin propulsion system increases thrust and reduces air consumption by up to 40%.
• 100% natural rubber construction provides flexibility, strength, and consistent performance across temperature ranges.
• Designed for low drag and reduced leg strain during extended missions.
• Spring straps for a secure and ergonomic fit with drysuit or wetsuit boots.
• Compact hydrodynamic design for helicopter and surface insertion operations.
• Proven in all forms of military diving: MCT, MTO, MCM, and UBDR.
• The Apollo Bio-Fin Pro XT ~15% harder compound providing stronger kick response and improved performance in high-current conditions.

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The World's No.1 Fin

Voted "BEST OVERALL" (2001-2007) and "TESTER'S CHOICE" (1999-2007) in Rodale / Scuba Lab USA's annual independent fin review.
The only open heel fin rated EXCELLENT for power vs. stress.
Award winning history.
The only split-fins voted Tester's Choice 8 years in a row!

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Material: 100% natural rubber (+15% Hardness vs Standard Pro)
Strap Type: Stealth Black Spring Strap with Black Heel Protector
Fin Type: Split-Fin
Finish: Stealth Black
Weight: Approx. 1.5 kg per pair
Brand: Apollo

Operational Information

• Operational Compatibility: Compatible with all military and commercial fin retainers, spring strap upgrades available (Bio-Fin Pro Stealth).
• Applications: Maritime Counter-Terrorism (MCT), Maritime Tactical Operations (MTO), Mine Counter-Measures (MCM), and Underwater Battle Damage Repair (UBDR).
• Maintenance: Rinse in fresh water after use; avoid prolonged UV exposure.
• Field Performance: Tested for helicopter drops and diver insertions; maintains propulsion efficiency in both surface and sub-surface operations.

XT High Hardness Variant - OP Benefits

• Enhanced Thrust Output: Increased stiffness improves direct power transfer from foot to blade, delivering stronger forward propulsion per kick cycle.
• Improved High-Current Performance: Greater blade resistance provides better control and propulsion authority in swift currents and tidal flow environments.
• Stronger Kick Feedback: Firmer response improves tactile control and propulsion precision during manoeuvring and load-bearing swims.
• Reduced Energy Loss: Minimises blade over-flex under high load, maintaining propulsion efficiency during aggressive finning.
• Improved Transition from Paddle Fins: Familiar resistance profile for divers accustomed to traditional paddle-style fins.

Codification Data

APOLLO SKU	NSN	Size	Length (mm)	USA Size	UK Size
FN02000B	4220-66-162-9391	M	300	8-9	7-8
FN02005B	4220-66-162-9392	L	300	9	8-8.5
FN02010B	4220-66-162-9393	L	325	9-10	8-9
FN02015B	4220-66-162-9394	L	350	10-11	9-10
FN02017B	4220-66-162-9395	L	375	11	10
FN02019B	4220-66-162-9396	XL	300	11	10
FN02020B	4220-66-162-9397	XL	325	11-12	10-11
FN02030B	4220-66-162-9397	XL	350	12-13	11-12
FN02035B	4220-66-162-9399	XL	375	14 up	13 up

BIO FIN SPRING STRAP KIT

No.	APOLLO SKU	OEM SKU	DESCRIPTION
1	SP92736	1551000025	250mm Spring Strap Kit, XS
2	SP92750	1551000027	275mm Spring Strap Kit , S
3	SP92735	1551000030	300mm S/Strap Kit , M
4	SP92751	1551000032	325mm S/Strap Kit , L-XL
5	SP92752	1551000035	350mm S/Strap Kit, XXL

BIO FIN SPRING STRAP SCHEMATIC - 1

No.	APOLLO SKU	OEM SKU	DESCRIPTION
1	SP92780	2500180010	Spring Strap Buckle Assembly BK (Pair)
2	SP92745B	350-20-80-301	Heel Protector For S/Strap Black Each
	SP92770	2500180011	250mm Spring Strap, Black, Each
	SP92771	2500180013	275mm Spring Strap, Black, Each
3	SP92772	2500180012	300mm Spring Strap, BK, Each
	SP92773	2500180014	325mm Spring Strap, Black, Each
	SP92774	2500180015	350mm Spring Strap, BK, Each
	SP92775	2500180016	375mm Spring Strap, BK, Each

BIO FIN SPRING STRAP SCHEMATIC - 2

No.	APOLLO SKU	OEM SKU	DESCRIPTION
1	SP92737B	3990180001	Bio Fin Screw (Black)
2	SP92738B	3521180011	Bio Fin Outer Plate Black
3	SP92758	3523900002	Spacer Base for Strap Holder 1.5mm/PVC BLACK
4	SP92741B	3502090002	SPRING HOLDER TOP COVER BLACK
5	SP92749B	3502090005	SPRING HOLDER BASE BLACK
6	SP92744	2502080412	Hold pin TYPE-2 K

How the BIO-FIN Works

The Apollo Bio-Fin delivers enhanced lift and propulsion while requiring reduced diver effort, resulting in greater efficiency and power output per kick cycle.
Unlike traditional flat-blade fins that simply push water vertically, the Bio-Fin generates forward thrust and hydrodynamic lift on both the upstroke and downstroke. Its engineered blade profile channels water smoothly across the leading and trailing edges, optimising flow dynamics.
The result is controlled lift and accelerated forward movement, operating on principles similar to an aircraft wing to maximise propulsion efficiency.



Fin Stroke Efficiency
The Bio-Fin’s 20º blade angle aligns with the diver’s natural knee and ankle flex, allowing the fin to work with the body rather than against it.
This reduces strain, enhances propulsion efficiency, and improves overall comfort. Apollo’s material selection and engineered blade profile provide fast acceleration and high power output while maintaining low fatigue. 




Ergonomic Design
Engineered with a propeller-like action, the Bio-Fin provides superior efficiency over traditional paddle fins.
This design maximises thrust while lowering energy expenditure, enhancing both speed and control. Independent field evaluations confirm that divers can reach and sustain higher
speeds with the Bio-Fin than with standard fin designs.