How to Size a Ski Race Back Protector: C7 to Tailbone Method

• Posted on 13 August 2026
• 0

Learn the C7 to tailbone method for sizing a ski race back protector, plus how to recheck fit as a junior racer grows through the season.

The correct way to size a ski race back protector is to measure from the C7 vertebra, the bony bump at the base of the neck, down to the tailbone. That measurement, not age or shirt size, determines which size protector actually covers the spine the way it is designed to.

Getting this measurement right matters more for junior racers than almost any other piece of gear, since a protector that is too short leaves the lower back exposed, and one that is too long rides up during a fall instead of staying in place.

Why C7 to tailbone, not height or age

Manufacturers size back protectors by torso length, not overall height, weight, or age. Two racers who are the same height can have very different torso lengths depending on build, so a size chart based on height alone is only a starting point. The C7 to tailbone measurement is the number that actually predicts whether the protector will cover the spine correctly.

C7 is the vertebra at the base of the neck that sticks out noticeably when your racer tips their head forward. It is the same landmark used to size motorcycle and mountain bike back protectors since the coverage requirement is the same: protect the length of the spine most exposed to impact.

How to take the measurement

1. Have your racer stand up straight in a t-shirt, without a jacket or race suit.
2. Ask them to tip their chin down toward their chest. The bump that pops out at the base of the neck is C7.
3. Place the end of a soft measuring tape at C7.
4. Run the tape straight down the spine to the tailbone, the bony point at the very base of the spine.
5. Record the number in inches or centimeters and match it against the brand's size chart, since sizing bands vary by manufacturer.

Two people measuring the same racer can get slightly different numbers depending on posture, so measure twice and use the shorter of the two readings if they differ by more than half an inch.

What the size ranges generally look like

Back protector size charts are built around this same C7 to tailbone measurement, typically broken into 5 to 6 bands from extra small through extra large. Junior sizes usually cover torso lengths from about 9 to 15 inches, with adult sizing starting above that. Because these bands vary by brand and by protector style, always check the specific size chart for the protector your racer is trying, rather than assuming sizes are interchangeable across brands.

The Atomic Live Shield AMID Lite Vest Jr, sized specifically for growing junior racers.

Sizing for a growing junior racer

Junior racers can move up a full size in a single season, especially during growth spurts between ages 10 and 14. A few practical notes for families:

• Recheck the measurement at the start of each season, not just when a protector visibly stops fitting.
• Buy for the current measurement, not projected growth. A protector that is too big will not stay in place during a fall, which defeats the purpose of wearing one at all.
• Watch for riding up during training, not just at rest. A protector that measures correctly on a chart but shifts during skiing may need a size down or a model with more strap adjustment.
• Adjustable straps buy you time, but they cannot fix a protector that is fundamentally the wrong length for your racer's torso.

The POC Pocito VPD Air Vest is built for the smallest junior torso lengths.

Checking fit with the race suit on

A back protector should be sized and checked with the race suit your racer actually wears, not on its own. Have your racer put the protector on, then the suit over it, and check two things: that the protector does not bunch or fold under the suit, and that the suit still allows a full range of motion through a tuck position. If either is off, size down on the protector before sizing up on the suit, since a looser suit will not fix a poorly fitted protector underneath it.

This is also where certification and fit intersect with the FIS back protector regulations guide, since speed-event programs sometimes specify coverage requirements on top of general sizing, and it is worth checking both before race day.

Frequently Asked Questions

What size back protector do I need?

Measure from the C7 vertebra at the base of the neck to the tailbone, then match that number to the manufacturer's size chart. Height and age are rough guides at best.

What if my racer measures between two sizes?

Size down if the protector has adjustable straps, since a slightly snug fit stays in place better than a loose one. Size up only if the shorter option leaves the lower back uncovered.

Does the race suit change what size protector I should buy?

No, size the protector to your racer's C7 to tailbone measurement first, then confirm it sits properly under the suit. Sizing the protector to fit the suit instead of the body can leave gaps in coverage.

How often should I remeasure a junior racer?

At the start of every season at minimum, and again mid-season if your racer has grown noticeably or the protector starts to feel snug across the shoulders.

Can I use an adult size chart for a smaller adult racer?

Yes, once your racer's C7 to tailbone measurement falls into an adult size band, use the adult chart. The measurement matters more than the age label on the size chart.

If you are not sure how a measurement translates to a size, our team can measure your racer in person and check the fit against their current suit. Browse our full junior and adult back protector selection, including sizing help on our back protector buying guide for parents, or pair your protector with a properly fitted set of forearm guards for full coverage. Stop in or call ahead and we will size your racer before you buy.