SIDE BY SIDE

Compare products.

See prices, running costs, specifications and trade-offs side by side. Choose two to four products of the same type.

Change products

Product 1Product 2Product 3 (optional)Product 4 (optional)

Fitness band

Amazfit Helio Strap

Black, nylon strap with hook-and-loop closure for 145 to 205 mm wrists

$99.99US price, checked Oct 23, 2026

Screen-free $99.99 band with no required subscription and up to 10 days of battery

Check price at Amazfit Full review →

Fitness band

Google Fitbit Air

Classic edition with the Obsidian band, including 3 months of Google Health Premium

$99.99US price, checked Oct 13, 2026

Screen-free $99.99 fitness band with up to 7 days of battery

Check price at Google Full review →

Criterion	Amazfit Helio Strap	Google Fitbit Air
US price	$99.99Checked Oct 23, 2026 · Price details in the review	$99.99Checked Oct 13, 2026 · Price details in the review
Three-year ownership estimate	$99.99 Incomplete known subtotal. Not included: energy use.	$99.99 Incomplete known subtotal. Not included: energy use.
Choose if	You want screen-free sleep, heart rate and recovery tracking, or an upper-arm heart rate source, for $99.99 with no required fee.	You want sleep, heart rate and blood oxygen tracking for about $100 from a 12 g band with no screen.
Main trade-off	There's no display, no charging cable in the box, and one reviewer saw heart rate readings about 10 bpm high on some long runs.	You read everything in the app, and Google's coach costs $9.99 a month after the 3 free months.
Key specifications	Battery life: Up to 10 days in typical use, according to Amazfit. That assumes all-day wear with continuous heart rate and blood oxygen tracking. It also assumes 8 hours of sleep breathing monitoring, stress monitoring and three 60-minute workouts a week linked to phone GPS. The battery is 232 mAh, and Amazfit gives no charge time. TechRadar's reviewer had 35% left after a week. Sensors: BioTracker 6.0 optical sensor (5 photodiodes and 2 LEDs), accelerometer, gyroscope and temperature sensor. Bluetooth 5.2. Health tracking: Heart rate every second, blood oxygen, stress, sleep stages including REM, sleep heart rate variability, naps, sleep breathing quality and a sleep score. Also the PAI health score and heart rate recovery. Overnight skin temperature changes are also shown. Training: More than 50 sports modes, with recognition of 25 strength exercises in strength training mode. It stores up to 21 days of heart rate data. It can broadcast live heart rate over Bluetooth to compatible Amazfit and third-party watches, gym machines, bike computers and apps. Workouts sync to Strava, TrainingPeaks (via Terra), adidas Running, komoot, Relive, Google Fit and Apple Health. Display and alerts: No display. You read everything in the Zepp app. Up to 10 vibration alarms, which are weak. Subscription: None required, according to Amazfit. The Zepp app is free. Zepp Aura is optional. Its free tier has sleep music, guided meditation and one message a day to an AI sleep assistant. Premium adds unlimited AI messages, weekly and monthly sleep reports and a larger music and meditation library. It costs $11.99 a month or $69.99 a year after a 14-day free trial. Water resistance: 5 ATM (50 m) under ISO 22810:2010. Amazfit says it suits splashes, showering and swimming. It advises removing the strap for hot showers and saunas, because steam can affect the seal. Wear: Wrist or upper arm. Amazfit says the upper-arm position helps reduce movement interference during hard training.	Battery and charging: Up to 7 days per charge. A full charge takes about 90 minutes, and 5 minutes gives about a day. Google suggests charging every few days to keep tracking without gaps. It doesn't publish the test conditions behind the 7-day figure. Sensors: Optical heart rate monitor, 3-axis accelerometer and gyroscope, red and infrared sensors for blood oxygen, a device temperature sensor and a vibration motor Health tracking: 24/7 heart rate, plus resting heart rate, heart rate variability, breathing rate, blood oxygen and skin temperature variation. It counts steps, Active Zone Minutes, distance and calories, and gives a Sleep Score with sleep stages, a Readiness score and Cardio Load. Google says it looks for signs of AFib while you're still or sleeping. It lists high and low heart rate alerts and Irregular Rhythm Notifications as Health Guardian features. Display: Google's spec sheet lists no display. You see your data in the Google Health app. Water resistance: Water resistant to 50 m. Google advises drying the band fully after it gets wet or sweaty. Subscription: 3 months of Google Health Premium are included. After that, Premium costs $9.99 a month. TechCrunch reported in May 2026 that a yearly plan costs $99, but Google's page doesn't show it. You must be at least 18 to enroll. What Premium adds: A personal coach built with Gemini, adaptive fitness plans, detailed sleep insights, daily guidance and advanced Health Guardian features. It also adds nutrition and cycle-aware coaching, a content library, and workout and mindfulness videos. What stays free: Activity and sleep tracking, Readiness, Cardio Load and the standard Health Guardian alerts are free in the app. Compatibility: Android 11 or later, or iOS 16.4 or later, with a Google Account and the Google Health app. Connects over Bluetooth 5.0. Google says it's intended for ages 13 and up.
Exact variant	Black, nylon strap with hook-and-loop closure for 145 to 205 mm wrists	Classic edition with the Obsidian band, including 3 months of Google Health Premium
Dimensions	Amazfit lists the tracker at 33.97 x 24.3 x 10.59 mm without the sensor, and 20 g. TechRadar's review gives 20 g with the band. The nylon strap is 22 mm wide and fits wrists from 145 to 205 mm around. The body is fiber-reinforced polymer.	The tracker is about 34.9 mm long, 17 mm wide and 8.3 mm high (1.4 × 0.7 × 0.3 in). It weighs 5.2 g on its own and 12 g with the band. Google lists the textile and polyurethane band as one size for 130–210 mm wrists.
Installation	No installation. You pair it with the free Zepp app on an iPhone running iOS 15.0 or later or an Android phone running 7.0 or later. In the box are the strap with the tracker fitted, a magnetic charging head and a manual. Amazfit says the USB-C charging cable isn't included. The packing list has no armband, and Amazfit lists a Helio Armband as a separate accessory.	No installation. You need a smartphone, a Google Account and the Google Health app, which runs on Android 11 or later and iOS 16.4 or later. It syncs over Bluetooth 5.0 at up to 30 ft. Syncing also needs an internet connection and location permission on your phone. In the box are the tracker, a wristband and a USB-C charging cable. If you already pay for Premium, cancel it before setup so the included months can start.
Materials	The body is fiber-reinforced polymer, and the strap is nylon with a hook-and-loop closure. TechRadar's review describes the central part as plastic with no metal and says it doesn't feel premium.	Google says the housing is recycled polycarbonate and PBT plastic. The band is textile with a stainless steel buckle, and the Obsidian band's buckle is matte black. The packaging is 100% plastic-free.
Warranty	One year from the date of original purchase, per Amazfit's US warranty policy. It covers products bought from Amazfit's official US online store, not other sellers. Amazfit repairs or replaces the device at its option, or may refund the purchase price, and you pay to ship it to Amazfit. A repaired or replaced device is covered for the rest of the year or 90 days, whichever is longer. The warranty excludes normal wear and tear, misuse, accidents and use for medical, healthcare or treatment purposes.	Google doesn't publish a Fitbit Air warranty length. Its Fitbit Limited Warranty page says Fitbit devices bought on or after July 11, 2023 are covered through the Google Hardware Warranty Center, which doesn't name the Air. The older Fitbit terms cover new products for one year from purchase. They exclude accidental damage, consumables such as batteries, normal wear and cosmetic damage such as scratches.
Returns	30 days from the purchase date to request a full refund, with a return authorization from Amazfit. Request the authorization by email or phone within the 30 days, then send the product back in the same condition, with all accessories and original packaging, at your own shipping cost. Amazfit can refuse a return that arrives without an authorization or all parts, or charge a 15% restocking fee or the value of missing accessories, whichever is higher. Orders placed in November and December can be returned through Jan 31 or for 45 days, whichever is longer. Shipping, handling and taxes aren't refundable, and refunds are paid within 4 weeks of Amazfit receiving the product.	Google Store Help says most items can be returned within 15 days of the day you receive them. Reset the device to factory settings before sending it back. For a refund, it goes back in its original box with all accessories and documentation. The Fitbit Air page advertises free shipping and returns, and the help page doesn't mention restocking fees.
Unresolved questions	Peer-reviewed accuracy data for the Helio Strap's heart rate, HRV, blood oxygen and sleep stages Charge time, charger power draw and battery lifespan The price of the Helio Armband for upper-arm wear How Amazfit handles replacement of a worn-out battery outside the one-year warranty	The US warranty length for Fitbit Air, since Google's Hardware Warranty Center doesn't name it Whether the free months roll into a paid Premium plan Which Health Guardian features count as advanced and need Premium Whether Fitbit Air's AFib alerts are FDA-cleared, since the 2022 clearance lists older Fitbit devices, not the Air Independent accuracy data for Fitbit Air's heart rate, blood oxygen and sleep tracking Test conditions behind the 7-day battery figure Charger power draw and battery lifespan

These comparisons use published specifications, not head-to-head tests. Prices and terms are dated. Unknown costs are not zero. Check the exact variant before you buy.