G-SHOCK 5000 & 5600 Series
The Original Square

Two hundred prototypes and a softball

Ibe’s first instinct was to wrap the entire watch in soft, flexible material. It didn’t work. No matter how much rubber he packed around it, the internals broke on impact. Worse, the more cushioning he added, the bigger the watch got. One early prototype was the size of a softball.

He eventually designed a five-stage shock-absorbing structure — five layers of cushioning between the outside world and the module. That solved the size problem, but created a new one: strengthening one internal component caused a different one to fail. Fix the crystal, the circuit board cracks. Reinforce the board, the LCD breaks. He’d throw a prototype from a third-floor window, walk downstairs, pick it up, analyse what broke, fix it, and throw the next one. This went on for months.

The rubber ball

Development stalled. Ibe gave himself one final week — every waking hour devoted to cracking the problem. He later said he thought he might have to leave the company if it didn’t work. The last day came. Nothing.

He stepped into a park next to the office and watched children bouncing a rubber ball. The ball hit the ground hard and the impact never reached the inside. That was the breakthrough: the module — the heart of the watch — shouldn’t be bolted rigidly to the case. It should float inside it, suspended at minimal contact points, the way air sits inside a ball. Impact hits the outside, the module barely notices.

Hollow case structure

The original used urethane resin — flexible enough to absorb impact, strong enough to protect, light enough to wear. That’s still the foundation on resin models.

All-directional covering

The uneven surface of the case and bezel guards buttons and glass from direct hits. The strap connects to the case in a curve so impacts don’t transfer straight to the case back.

Reinforced inner case

Metal replaced by glass fibre-reinforced resin for the inner case — strong, light, and easier to work with. This opened the door for solar panels, Bluetooth antennas, radio receivers, and heart rate sensors without compromising the shock-resistant shell.

All-metal structure

Fine-resin buffers sit between the forged bezel and centre case. A three-pronged strap connection disperses shock through the connecting pipes. Full stainless steel that still passes the same drop tests as the resin original.

Carbon Core Guard

Carbon fibre-reinforced resin inner case. Lighter and stronger than standard resin, built to protect the module from both drops and sustained vibration.

Compact square

The same architecture scaled down into a slimmer case for smaller wrists. Same toughness, different fit.

Shock-resistant + 20-bar water resistance

The foundation. Built for strenuous sports, swimming, surfing, and everyday life without a second thought.

1996 — EL backlight

Replaced the old micro-bulb. Later came auto-light (tilt your wrist, the display lights up) and high-brightness LED.

2002 — Tough Solar

Casio’s solar charging system turns any light source into power. No battery changes.

2005 — Multi-Band 6

Radio sync picks up atomic time signals from up to six transmission stations worldwide and corrects the watch automatically.

2008 — Sports functions

Interval timers, tide graphs, moon data, low-temperature resistance down to −20°C.

2012 — Bluetooth Smartphone Link

Pair the watch to your phone for automatic time adjustment and app-based settings management.

2023 — Heart rate monitor

An optical sensor in the case back tracks heart rate in real time during exercise and daily wear.