Casio F-91W vs Casio G-Shock GA-B2100 CasiOak
Casio's timepiece meets Casio's diver
Quick Verdict
The Casio F-91W (Under $50) offers Casio Digital Quartz (Battery) precision in the tier below the Casio G-Shock GA-B2100 CasiOak ($100–$150). The F-91W measures 35mm and is rated 30m (Splash Resistant). The G-Shock GA-B2100 CasiOak counters with Made in Japan craftsmanship and 200m (20 ATM) water resistance. Both are exceptional watches for their respective tiers.
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Specifications Compared
| Feature | Casio F-91W | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Price | Under $50 | $100–$150 |
| Case Size | 35mm | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) |
| Movement | Quartz Module 593 | Quartz Module 5689 (Tough Solar + Bluetooth) |
| Caliber Type | Casio Digital Quartz (Battery) | Casio Quartz (Solar-Powered) |
| Power Reserve | 7-Year Battery | About 7 months on a full charge without light; about 18 months in power-saving (Casio) |
| Water Resistance | 30m (Splash Resistant) | 200m (20 ATM) |
| Crystal | Acrylic | Mineral Glass |
| Case Material | Resin | Carbon Core Guard Resin |
| Origin | Casio (Japan) | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Casio's design language vs Casio's approach
The Casio F-91W features a Resin case at 35mm with Acrylic protection. The Casio G-Shock GA-B2100 CasiOak offers Carbon Core Guard Resin construction at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with Mineral Glass. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Quartz Module 593 vs Quartz Module 5689 (Tough Solar + Bluetooth)
The F-91W runs the Quartz Module 593 (Casio Digital Quartz (Battery), 7-Year Battery power reserve) at standard frequency. The G-Shock GA-B2100 CasiOak uses the Quartz Module 5689 (Tough Solar + Bluetooth) (Casio Quartz (Solar-Powered), About 7 months on a full charge without light; about 18 months in power-saving (Casio) reserve) at standard. Power reserves are closely matched.
Wearability & Fit
35mm vs 45.4mm (48.5mm lug-to-lug, 11.9mm thick) — different wrist presence
At 35mm, the F-91W wears more compactly on smaller wrists compared to the G-Shock GA-B2100 CasiOak at 45.4mm (48.5mm lug-to-lug, 11.9mm thick). Water resistance differs: 30m (Splash Resistant) vs 200m (20 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Casio F-91W sits at Under $50 and the Casio G-Shock GA-B2100 CasiOak at $100–$150. On the specs that outlast any price: the F-91W uses Acrylic with 7-Year Battery, against Mineral Glass and About 7 months on a full charge without light; about 18 months in power-saving (Casio) on the G-Shock GA-B2100 CasiOak. Service intervals are typically 5-7 years for both.
Water Resistance
30m (Splash Resistant) vs 200m (20 ATM)
The F-91W is rated to 30m (Splash Resistant) while the G-Shock GA-B2100 CasiOak handles 200m (20 ATM). The G-Shock GA-B2100 CasiOak offers superior water resistance.
Our Verdict
Casio
F-91W
Choose the Casio F-91W if you prioritize Casio Digital Quartz (Battery) engineering, Casio (Japan) craftsmanship, and 30m (Splash Resistant) water resistance. At Under $50, it delivers Quartz Module 593 with 7-Year Battery power reserve.
Check Price on AmazonCasio
G-Shock GA-B2100 CasiOak
Choose the Casio G-Shock GA-B2100 CasiOak if you value Casio Quartz (Solar-Powered) technology, Made in Japan heritage, and 45.4mm (48.5mm lug-to-lug, 11.9mm thick) proportions. At $100–$150, the Quartz Module 5689 (Tough Solar + Bluetooth) with About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Casio F-91W and Casio G-Shock GA-B2100 CasiOak represent two distinct approaches to fine watchmaking — the Casio bringing Casio (Japan) tradition while Casio delivers Made in Japan engineering.
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How This Page Was Made
Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.