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Nine open-heel blade fins for technical and professional diving — the Rubber Fins III series in black, yellow, pink, and red (108–131 €), the Rubber Fins IV series in black and yellow (108–117 €), and the premium Diva (126 €) and Retta (128 €) blade models. All open-heel fins are designed for use with drysuit boots or neoprene booties; the III and IV series ship with stainless steel spring straps as standard. Sizes S–XL. For a broader selection of recreational fins, see SoprasSub.
For more fins please check SoprasSub.
Open-Heel Blade Fins for Technical Diving
All nine fins in this range are open-heel paddle fins — the standard format for technical diving. An open heel accepts a drysuit boot or neoprene bootie of any thickness, which means the same fin works across all exposure protection setups without sizing issues. The foot pocket must grip the boot firmly: a loose fit wastes stroke energy and can allow the fin to rotate; a tight fit causes cramps on long dives. Try fins with the specific boot you dive in before committing to a size.
Rubber Fins III Series
The Rubber Fins III is the core technical fin in the Sopras Tek range. Full rubber blade construction provides a responsive, medium-stiff blade that delivers efficient thrust across frog kick, flutter kick, and back kick. The open foot pocket is sized for drysuit boots and thick neoprene booties. Available in four colours at two price points: black (108 €, sizes S/L) and yellow (117 €, sizes S/XL) are the multi-size variants; pink (131 €) and red (131 €) are single-size premium colour editions. All III variants ship with stainless steel spring straps installed.
Rubber Fins IV Series
The Rubber Fins IV is a second blade geometry variant in the same open-heel rubber construction format. The IV series features a modified blade channel and angle that alters the thrust delivery profile relative to the III — some divers prefer the IV’s stroke feedback, particularly for frog kick. Available in black (108 €, sizes S/M/L) and yellow (117 €, sizes S/M/XL). Both variants ship with stainless steel spring straps.
Diva and Retta
The Diva (126 €, SKU 405000) and Retta (128 €, SKU 408000) are the premium blade models in the Sopras Tek range. Both are single-SKU fins with a refined blade geometry designed for higher propulsion efficiency and precision. The Diva and Retta are single-size models — confirm sizing before ordering. These are the appropriate choice for experienced technical divers prioritising blade performance over the broader size range available in the III and IV series.
Omega
The Omega (56 €, SKU 414000/0-2) is the entry-level open-heel fin in the range — a more flexible blade at a significantly lower price point. Multiple size variants are available. The Omega is suited to recreational or training contexts where the full blade stiffness of the III/IV series is not required.
What to Look For
- III vs. IV blade geometry: The primary difference is blade channel design and angle, which changes how thrust is delivered through the kick cycle. Both are mid-stiff rubber blade fins. If possible, test both in a pool with the boots you dive in — individual kicking style determines which performs better for a specific diver.
- Size with your boot: Open-heel fin sizing is based on the boot size, not bare foot size. The foot pocket must close firmly around the boot without the spring strap doing most of the clamping work. Try the fin on with your actual diving boot before purchasing.
- Spring strap quality: All III and IV fins ship with stainless steel spring straps. These are 316 SS for corrosion resistance in saltwater. The attachment points (buckle tabs on the fin foot pocket) should be inspected periodically — the strap itself is durable but the tab-to-pocket junction can develop wear over extended use.
- Replacement spring straps: The S.S. spring strap (38 €) and S.S. buckle for fins (40 €) in the Accessories category are the correct replacement hardware for fins in this range. Sizes S/M/L/XL/Z — match to your fin foot pocket width.
Maintenance and Care
Rinse fins with fresh water after every saltwater dive, including inside the foot pocket and around the spring strap attachment tabs. Store flat or hanging — do not stack heavy equipment on top of fins as sustained pressure can permanently deform the blade. Inspect the blade edge and the blade-to-foot-pocket junction for stress cracks after every season of heavy use; this junction is the highest stress point on a rubber blade fin. Check spring strap coils for corrosion and the end tabs for wear at each end annually; replace spring straps at the first sign of deformation or corrosion pitting.
FAQ
How stiff should my fins be for technical diving?
Stiff enough to deliver efficient thrust at the kick rate you dive — not so stiff that you are fighting the blade on every stroke. The Rubber Fins III and IV are mid-stiff blades suitable for most technical divers. Divers with strong legs and a powerful frog kick may prefer the stiffer end of the range; divers covering long distances at low effort may prefer a slightly softer blade. Test in a pool under gear load before diving on a technical profile.
Can I use these fins with drysuit rock boots?
Yes — open-heel fins are designed for use with boots. The foot pocket on the III and IV series accommodates standard drysuit rock boots. Confirm the fin size against the boot size with the boot actually in the foot pocket — rock boots add significant bulk compared to neoprene booties and may require a larger fin size than expected.
Why are the pink and red III fins more expensive than black?
The black and yellow III variants are available in multiple sizes (S/L and S/XL respectively) at lower per-unit cost. The pink and red III fins are single-size specialty colour editions with a higher per-unit price reflecting the smaller production volume. If size range is important, the black or yellow variants provide more flexibility.