G-Shock has spent over 40 years perfecting the art of the rugged digital watch. One could argue they have long achieved it and are now primarily focused on making it more fun. The latest example is the new HIDDEN GLOW collection, which comprises the GA2100HD-8A and the DW6900HD-8. At first glance, they may look like the classic 2100 and 6900-series references we’ve come to know and love, but a closer look (in the dark) reveals something special.

The GA2100HD-8A and DW6900HD-8 are 45.4mm and 50mm wide, respectively, and wear reasonably thanks to their lightweight resin cases and famously compact G-Shock feeling. Both watches feature matte gray cases and bezels, which Casio uses to highlight this collection’s trick: glow-in-the-dark dials. The black and white dials (digi-analog on the 2100 and purely digital on the 6900) are made of phosphorescent elements that glow green in low light. The result is a striking effect that emphasizes each model’s distinct dial layout and design.

The 6900-series contains all the G-Shock bells and whistles: chronograph, calendar, alarm, and a special flash alerting feature. The 2100-series includes all of that and trades the flash alert for a full world timer with 31 time zones. Both watches are powered by battery-operated quartz movements rated to /- 15 seconds a month.