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Casio G-Shock GA-B2100 vs Casio G-Shock GA-B2100C-9A

These are the same watch. The GA-B2100-3ADR and GA-B2100C-9A share the module, the Carbon Core Guard case, Tough Solar, Bluetooth and 200-meter water resistance. The only real difference is color: the 3ADR is green with a black dial, the C-9A is yellow. Buy whichever color you will actually wear. Owners of the 2100 line praise the slim 11.9 mm case, the light 52 g weight and the solar charging that ends battery swaps.

  • Choose the GA-B2100-3ADR if you want the green case and band with a black dial, which reads more subdued than the yellow.
  • Choose the GA-B2100C-9A if you want the bright yellow finish that stands out and matches the classic G-Shock 5600 palette.

Prices

  • Casio G-Shock GA-B2100: $134.99 at Amazon (last seen Nov 8)
  • Casio G-Shock GA-B2100C-9A: $109.24 at Mercari (checked today)
  • Difference: the Casio G-Shock GA-B2100C-9A is $25.75 cheaper than the Casio G-Shock GA-B2100 at the latest prices (Nov 8 and Nov 10)
Casio
Casio G-Shock Watch - GA-B2100-3ADR Black Dial, Green Band

Casio G-Shock GA-B2100

Casio G-Shock Watch - GA-B2100-3ADR Black Dial, Green Band

$134.99at AmazonChecked Nov 8
See all prices and details
Visit Amazon

As an Amazon Associate, Deal.ai earns from qualifying purchases.

Pros
  • Green and black colorway is easy to wear daily
  • Tough Solar ends battery replacement
  • Slim 11.9 mm case and 52 g weight sit flat on the wrist
  • 200 m water resistance and shock resistance for rough use
Cons
  • Green band can show fading with heavy sun exposure
  • Mineral glass scratches more easily than sapphire
  • Negative LCD display is harder to read at angles
Casio
Casio GA-B2100C-9A

Casio G-Shock GA-B2100C-9A

Casio GA-B2100C-9A

$109.24at MercariChecked 3 h ago
See all prices and details
Visit Mercari
Pros
  • Bright yellow finish is easy to spot and matches classic G-Shock colors
  • Same solar, Bluetooth and Carbon Core Guard build as the green model
  • Dual Illuminator with afterglow and selectable duration
  • 200 m water resistance and shock resistance
Cons
  • Yellow draws attention and clashes with formal wear
  • Mineral glass scratches more easily than sapphire
  • Negative LCD display is harder to read at angles

What separates them

Casio G-Shock GA-B2100Casio G-Shock GA-B2100C-9A
ColorwayGreen case and band, black dialYellow case and band, styled to be noticed
Module and functionsTough Solar, Bluetooth, 5 alarms, 1/100 s stopwatch, 60 min timer, world timeSame module: Tough Solar, Bluetooth, 5 alarms, 1/100 s stopwatch, 60 min timer, world time
Case and buildCarbon Core Guard, resin case, mineral glass, 48.5 x 45.4 x 11.9 mm, 52 gCarbon Core Guard, resin case, mineral glass, same dimensions and weight
Water resistance200 m200 m
LightingDouble LED lightDual Illuminator LED with afterglow, 1.5 or 3 second duration
Battery lifeAbout 7 months normal use, 18 months with power save in darknessAbout 18 months with power save in darkness
Visibility and stylingMuted green suits office and outdoor wearHigh-visibility yellow draws attention

Price history

$154.27$90.00
Nov 8Nov 10
  • Casio G-Shock GA-B2100: lowest $90.00 on Nov 8 at CASIO; $90.00 on Nov 10.
  • Casio G-Shock GA-B2100C-9A: lowest $109.24 on Nov 10 at Mercari.

Prices at every store

Casio G-Shock GA-B2100

  • i-watchNew

    In stockReturn policy

    $231.00Checked Nov 8
    Visit i-watch
  • The Casio ShopNew

    In stockShips from South Africa · priced in ZAR (ZAR 3,994.00) · duties may applyReturn policy

    $241.50Checked Nov 8
    Visit The Casio Shop
  • AmazonNew

    Availability unknown

    As an Amazon Associate, Deal.ai earns from qualifying purchases.

    $134.99Free shippingChecked Nov 8
    Visit Amazon
  • CASIONew

    Out of stock

    $90.00Free shippingChecked 3 h ago
    Visit CASIO

Store links may earn us a commission. Some prices via Klarna.

All 4 stores and price history →

Casio G-Shock GA-B2100C-9A

  • MercariNew

    In stock

    $109.24Checked 3 h ago
    Visit Mercari
  • Market Cross JewellersNew

    In stockReturn policy

    $126.21Checked Nov 8
    Visit Market Cross Jewellers
  • JuwelierBektasNew

    In stockShips from Germany · duties may applyReturn policy

    $138.00Checked Nov 8
    Visit JuwelierBektas
  • MonawatchNew

    In stockMade for another market

    $137.00+ $32.70 shippingChecked 3 h ago
    Visit Monawatch

Also available at

  • eBayCheck price at eBay

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All 27 stores and price history →

Specs compared

SpecCasio G-Shock GA-B2100Casio G-Shock GA-B2100C-9A
Case size48.5 × 45.4 × 11.9 mm—
Weight52g—
Water resistance200-meter water resistance—
Battery operating time7 months on rechargeable battery—
Power save runtime18 months on rechargeable battery—
Accuracy±15 seconds per month (with no mobile link func…—
World time38 time zones (38 cities + coordinated universa…—
Stopwatch1/100-second stopwatch—
Countdown timer60 minutes—
Alarms5 daily alarms—
Case materialCarbon / Resin—
Band materialResin Band—

What reviewers say

Casio G-Shock GA-B2100

Owners of the GA-B2100 line praise the slim case, solar charging and the octagonal look, and most find it comfortable for daily wear. Common complaints are the mineral glass, the resin band's long-term durability and the fiddly app pairing.

What people mention
  • Size and weightPraisedOwners say the slim, light case wears comfortably and slips under a cuff.
  • Solar chargingPraisedReviewers like that Tough Solar removes the need for battery swaps.
  • GlassCriticisedSome owners report scratches on the mineral glass with normal use.
  • Band durabilityCriticisedA few long-term owners say the resin band cracks or fades over time.

Casio G-Shock GA-B2100C-9A

Owners of the B2100 line generally praise the slim case, solar charging and Bluetooth timekeeping, and many call it the best-value modern G-Shock. The most common complaints are the resin strap feeling stiff or cheap and the busy analog-digital dial being hard to read at a glance.

What people mention
  • Solar chargingPraisedOwners like that light keeps it running and they never need to open the case for a battery.
  • Bluetooth syncPraisedPairing with the phone app is seen as a simple way to keep time accurate and find a misplaced phone.
  • Case sizePraisedThe slim Carbon Core Guard case is called comfortable and less bulky than classic G-Shocks.
  • StrapCriticisedSome owners find the resin band stiff and plain compared with the rest of the watch.

Questions and answers

Are these two watches actually different?
No. They use the same module, case and band materials. The colorway is the only difference, so pick the one you like looking at.
Which is better for swimming and surfing?
Both are rated to 200 meters and are shock resistant, so either works for swimming, surfing and snorkeling. Neither is a dive computer.
Which lasts longer?
Both run on Tough Solar and should last years without a battery change. Stored in darkness with power save on, each runs about 18 months on a charge.
Is the yellow one worth stepping up to?
There is no step up in hardware. Choose yellow only if you want the bolder look; you give up nothing in features.
Does either work with a smartphone?
Yes. Both pair over Bluetooth for accurate time, world time, reminders and a phone finder. Signal range is about 2 meters.
How readable is the display?
Both use a negative LCD, which is dimmer at steep angles than a standard positive display. The LED light helps in low light.

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More comparisons

  • Casio G-Shock 2100 Series GA-B2100-1A Men's Watch vs Casio G-Shock Watch - GA-B2100-3ADR Black Dial, Green Band
  • Casio G-Shock 2100 Series GA-B2100-1A Men's Watch vs Casio GA-B2100C-9A