Five shafts. Five very different golfers. All built on the same KHT carbon platform — but tuned to a different CPM frequency, a different weight, and a different feel profile. Choosing wrong costs you distance and feel. Choosing right can be the biggest equipment gain you've made in years.
This guide breaks down every AutoFlex SF Series model so you can find your number before you order.
Every AutoFlex shaft is rated in CPM — Cycles Per Minute — the objective measure of how many times a clamped shaft oscillates in one minute. Higher CPM = stiffer shaft. Lower CPM = more flex. Unlike letter grades (R, S, X), CPM tells you exactly what you're getting, regardless of brand or manufacturer.
| Model | Weight | CPM | Flex Label | Best Swing Speed |
|---|---|---|---|---|
| SF305X | 37g | 170 | Ladies / Senior | Under 70 mph |
| SF405 | 46g | 190 | Senior / A-flex | 70–85 mph |
| SF505 | 50g | 210 | Regular | 85–95 mph |
| SF505X | 54g | 220 | Stiff | 95–105 mph |
| SF505XX | 58g | 240 | Extra Stiff | 105+ mph |
The purple rows highlight the two most commonly fitted models — SF405 and SF505 together account for the majority of AutoFlex fittings. If you're unsure where you land, start there and we'll dial it in below.
Each SF model has a sweet spot — a swing speed window where CPM and shaft weight work together to maximize energy transfer. Going too stiff starves the shaft's KHT kickback. Going too soft creates timing problems and a loss of control.
Don't know your swing speed? Most golf retailers and driving ranges with a launch monitor can measure it for free in under five minutes. It's the single most useful number to know before buying any shaft.
Most golfers land between these two. Here's how to decide:
| You should choose SF405 if… | You should choose SF505 if… |
|---|---|
| Your swing speed is consistently under 85 mph | Your swing speed is 85–95 mph |
| You feel like your current shaft is fighting you | Your current regular-flex feels a bit loose |
| You want maximum carry from a smooth swing | You want carry + control at higher effort |
| You are a senior looking to replace a senior flex | You are a mid-handicap replacing a regular flex |
| You tend to hit high, soft shots already | You want a slightly more penetrating ball flight |
The 10-gram rule applies here too: The SF405 is 9 grams lighter than the SF505. All else equal, that weight difference translates to roughly 1 mph of additional swing speed — which is real carry distance for most golfers.
The X in SF305X doesn't mean Extra Stiff — it means eXtra light. The SF305X is the most flexible and lightest shaft in the lineup, designed for golfers who need maximum assistance from the shaft to generate clubhead speed. It's the opposite of what the X suffix means in conventional OEM shafts.
This naming convention trips up a lot of shoppers, so if you've been avoiding the SF305X because you thought it was stiff — it isn't. At 170 CPM and 37 grams, it's the most forgiving and distance-maximizing shaft in the SF family for slower-swing golfers.
The SF505X (220 CPM, 54g) and SF505XX (240 CPM, 58g) are built for faster swingers who want the benefits of KHT technology — lightweight construction, high energy storage, precise CPM calibration — without the excessive flex of the lower models.
At 105+ mph, the SF505XX is AutoFlex's answer for scratch and tour-level players. It delivers tour-caliber stability while still coming in lighter than most OEM extra-stiff options, which typically weigh 65–75 grams. That weight savings still contributes to clubhead speed without sacrificing shot-to-shot consistency.
Every AutoFlex SF shaft is frequency-matched to within ±2 CPM of its rated value during manufacturing. This means if you order an SF505 (210 CPM), your shaft will measure between 208 and 212 CPM on a frequency analyzer. That consistency is rare in the industry — most conventional shafts have tolerances of ±5 CPM or more.
CPM and weight tell you the objective story. But golfers also care about feel — the subjective sensation of load, release, and contact that changes how you perceive the shot.
AutoFlex has appeared in the bags of multiple tour professionals, which gives us real-world data on where the models land:
The range from Lee Trevino to Jimmy Walker to Adam Scott covers nearly the full SF spectrum — which tells you the lineup is genuinely diverse, not a one-size-fits-all product.
The most reliable way to choose your SF Series model is a CPM-based fitting at an authorized AutoFlex dealer. A fitter will measure your current shaft's CPM on a frequency analyzer, compare it to your swing speed and tempo, and map you to the SF model that matches.
If you don't have access to a fitter, use this quick self-guide:
All five SF Series models ship from autoflex.us with a 30-day exchange policy. If you're between models, order the lighter one first — it's easier to go stiffer than to fix a shaft that's fighting your swing.
Shop SF Series on autoflex.us ↗The right model is out there. The only wrong choice is playing a shaft that's working against you.