The Fitbit FB403BK-WMT Flex 2 is a sleek, waterproof activity tracker that has garnered a mix of praise and criticism from its users. Its compact size and waterproof feature make it a favorite for those who prefer a minimalist design and need a device that can withstand water exposure, such as during swimming.

Users appreciate the device's ability to send text and call alerts, which helps reduce phone usage. The silent alarms are particularly noted for their effectiveness, even for heavy sleepers. However, some users have reported issues with the step counter accuracy, noting it sometimes counts arm movements as steps.

Durability is another highlight, with several users mentioning they have used their Flex 2 for years without significant issues. The option to change bands easily allows for customization according to personal style or occasion.

On the downside, there are complaints about defective units that cannot be charged and difficulties in updating the device's software. Some users also miss features like stair tracking and detailed sleep analysis available in other models.

Overall, the Fitbit Flex 2 is best suited for those who prioritize simplicity and durability in a fitness tracker. While it may lack some advanced features found in newer models, its compact design and essential tracking capabilities make it a reliable choice for everyday use.