NW-S21

The NW-S21 is a second-generation sports S Series Walkman. It features 128MB built-in flash storage and supports MP3 and ATRAC3plus playback on a 1-line monochrome OLED display. A single AAA battery supplied up to 83 hours of runtime. This sport-oriented model derived from the NW-E90 and NW-E70 generation and continued the S Series focus on extended battery life for active use.

A second-generation sports S Series model that shows Sony beginning to tighten the identity of the active-use branch without yet turning it into a feature-heavy side family. The emphasis remained on compactness, endurance, and practical playback instead of richer interface or multimedia behavior. It reflects Sony's attempt to preserve a simple, long-lasting flash Walkman for movement and exercise while the broader line was becoming more varied and more stylistically segmented.