Siux Electra Stupa Pro ST4 2025

Technologies

Pros

• ✓The 15K carbon face on the 38mm frame delivers a direct, crisp response on the smash, with minimal energy loss when you connect near the frame.

Cons

• ✗The Hard EVA core demands a fully developed swing; with a short backswing or limited arm power, ball exit falls noticeably short compared to a medium or soft core.

Franco Stupaczuk is competing with the Siux Electra Stupa Pro ST4 2025 this season, one of the pro circuit's benchmark players. The racket sits within the Electra ST4 line, which Siux splits into three tiers — Pro, Elite and Go — by technical demand; the Pro is the most competition-ready of the three, with no compromises on materials.

The shape is hybrid, sitting between teardrop and diamond, with an even balance that spreads weight between head and handle rather than piling it all toward the tip. It's a deliberate design call so a competition-level player can smash with real force without sacrificing volley control or reaction speed at the net.

15K carbon face meets 38mm frame: the combo that stiffens every strike

The face is built from 15K carbon, a high fibre density that sits between the 12K used in mid-range lines and the 18K found in the stiffest rackets on the market. The result is a surface that barely flexes on impact: strike energy transfers almost entirely into the ball instead of bleeding away through material flex.

The 38mm frame is engineered for structural stiffness without piling extra weight onto the rim. Inside sits a Hard EVA core, the firmest rubber in Siux's range: high density, minimal deformation on contact, and a crisp response that sends the ball back faster than a medium or soft EVA — in exchange for demanding a swing that's already technically sound.

Both faces carry a sandy, rough finish that boosts friction with the ball at contact, most noticeable when brushing up on cut bandejas and adding spin on serve. On the maintenance side, the racket comes with Siux's Switch Strap system — a tool-free swappable wristband you can replace without touching the rest of the frame.

On-court feel: from víbora to the back of the court

On attacking shots — smash, víbora, bandeja — the 15K face and Hard EVA core combo makes itself known instantly: the ball exits fast with a crisp, dry sensation, none of the springy bounce you'd get from a softer rubber. It's the classic build of a competition racket aimed at players who already generate their own power and don't want the material eating into ball exit speed.

On defence and from the back of the court, the even balance keeps the racket from feeling as head-heavy as a pure diamond shape, making it easier to reset into a defensive stance between shots. That said, the core's firmness punishes anyone caught off balance or hitting with a stretched arm: without the cushioning of a softer EVA, a mishit shot is felt more sharply in the wrist and elbow.

At the net, the even balance and 38mm frame give a reasonable response on low volleys, though the racket's overall stiffness rewards anticipation: this isn't a build that forgives pure-reaction volleys the way a softer-core, low-balance model would.

Tech specs

Who is the Electra Stupa Pro ST4 built for?

It suits advanced-to-competition players who already generate their own power and want a racket that won't rob them of ball exit speed: attacking profiles with solid physical conditioning and a well-grooved smash.

It's not the best call for players still climbing the levels who need the racket to help produce pace with less effort, nor for anyone nursing elbow or wrist issues: the firmness of the Hard EVA core and the stiffness of the 15K face transmit more vibration on off-centre hits than a softer build would.

Verdict

The Siux Electra Stupa Pro ST4 2025 is a no-compromise competition racket: 15K carbon face, 38mm frame and Hard EVA core built to maximise ball exit speed. Its biggest strength is crisp power on attacking shots; its biggest catch is the physical demand it places on you when a shot isn't struck cleanly. Recommended for an advanced-to-competition player with an already well-formed smash, not for someone just starting to move up the levels.

What sets the Pro apart from the rest of the Electra ST4 line?

The Pro is the top tier of Siux's Electra ST4 range, carrying a more competition-focused material spec than the Elite and Go versions in the same family — built for the most demanding player among the three variants Siux offers under the Electra ST4 name.

How do you swap the Switch Strap wristband on this racket?

Siux's Switch Strap system lets you remove and replace the wristband without tools: release the anchor at the handle and click the new strap into place. It works both for hygiene and for matching wristband thickness to each player's hand, without needing to swap the whole racket.