Speedo Fastskin Hiro Cap Size Guide

This size guide covers the Speedo Fastskin Hiro Swimming Cap, available in sizes S, M and L. The Fastskin Hiro is a tight-fitting, moulded racing cap engineered to reduce drag and provide a secure, wrinkle-free fit during competition. Its thinner silicone construction and full gloss interior are designed for streamlined, grip-secure racing performance. It is fully approved by World Aquatics (FINA) for use in sanctioned competitions.

To find your correct size, measure the circumference of your head and the ear-to-ear distance over the top of your head using a soft measuring tape.

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How to Measure

Use a soft measuring tape held snugly against the skin. Take both measurements before comparing to the sizing table.

  • A
    Head Circumference Measure around the fullest part of your head, starting at the centre of the forehead, keeping the tape level and horizontal all the way around.
  • B
    Ear to Ear (over top) Measure from earlobe to earlobe over the top of the head, keeping the tape flat against the skull.

If your measurements fall between sizes, size up for added comfort.

Speedo Fastskin Hiro Cap
Speedo Fastskin Hiro Swimming Cap size guide
Sizing Table — Speedo Fastskin Hiro Swimming Cap
Measurement S — Small M — Medium L — Large
Head Measurements (cm)
A — Head Circumference ~53 cm ~58 cm ~63 cm
B — Ear to Ear (over top) ~33 cm ~38 cm ~43 cm

Measurements are approximate. The Fastskin Hiro is made from 100% silicone and has some stretch — if between sizes, size up.

Fit Notes — Speedo Fastskin Hiro Swimming Cap
  • The Fastskin Hiro should feel firm and close-fitting against the head with no air pockets, wrinkles, or gaps — this is essential for its drag-reducing performance during racing.
  • The cap is made from 100% silicone and will feel tighter than a standard training cap. The moulded construction is designed to conform to the contours of the head for the best possible seal.
  • When putting on the cap, hold it at both sides and stretch it over the head from front to back — avoid pulling from the front edges as this can distort the moulded shape.
  • Take care with fingernails and hair grips when putting on or removing the cap — the thinner silicone can tear if snagged.
  • If between sizes, size up — a cap that is too small is harder to put on, more prone to tearing, and will be uncomfortable during a race.
  • Rinse in cold fresh water immediately after every use. Store flat and dry, away from direct sunlight. Do not fold, roll, or compress the cap during storage as this can cause creasing that affects its shape.
  • Do not apply petroleum-based products, sunscreen, or hair products before putting on the cap — these can degrade the silicone over time.
  • Unsure? Contact our team or call +44 1827 330600.
Frequently Asked Questions — Speedo Fastskin Hiro Swimming Cap

Yes. The Speedo Fastskin Hiro Swimming Cap is fully approved by World Aquatics (WA/FINA) and is legal for use in all sanctioned competitive swimming events. Always check with your event organiser or club to confirm any additional local rules regarding cap use in competition.

Measure the circumference of your head starting at the centre of the forehead, and your ear-to-ear distance over the top of the head. Compare both measurements to the sizing table above. If your measurements fall between sizes, choose the larger size — a cap that is too small is harder to put on, more prone to tearing, and uncomfortable during competition.

The Fastskin Hiro is a moulded racing cap engineered specifically for competition. Unlike a standard silicone cap which simply stretches over the head, the Hiro's moulded construction holds its shape to provide a consistently streamlined, wrinkle-free profile in the water. The thinner material and full gloss interior further reduce drag and improve grip compared to a standard training cap.

The Fastskin Hiro is designed for hydrodynamic performance, not as a waterproofing device. While it significantly reduces water penetration compared to a standard cap, it is not completely waterproof. Water will still enter around the edges during swimming.

Hold the cap at both sides with both hands, place it at the front of the forehead, and stretch it back over the top and down the back of the head in one smooth motion. Avoid pulling from the front edges as this can distort the moulded shape. Check that there are no air pockets and that the cap sits flat all the way around.

Yes. The Fastskin Hiro is designed to fit snugly to achieve its drag-reducing profile — it will feel tighter than a standard training cap. This is normal and intentional. The silicone will ease slightly with regular use. If the cap feels painfully tight or leaves deep marks after a short time in the water, size up.

The Fastskin Hiro is a competition racing cap and while it can be worn during training, regular use will shorten its lifespan. Reserve it for races and competition warm-ups. For everyday training, a standard silicone cap is recommended.

Rinse thoroughly in cold fresh water immediately after every use to remove chlorine and salt. Allow to dry completely before storing. Store the cap flat, away from direct sunlight and heat. Do not fold, roll, or compress the cap as this can cause creasing that affects its shape and fit. Avoid contact with petroleum-based products, sunscreen, or hair products.