NW-S639F

The NW-S639F is the highest-capacity 16 GB model in the sixth-generation S Series Network Walkman family. It embodied the generation's unified design and playlist expansions. It offers 16 GB of flash storage for MP3, WMA, AAC, and WAV files along with the 240x320 LCD display, FM radio with recording, video and photo playback, Clear Audio Technology, and 40-hour lithium-ion battery life.

This Walkman model came from the period where the S Series had become polished, compact, and easy to understand inside the broader Walkman hierarchy. The line had not always been this settled. The S639F showed Sony finally stopping overworking the S concept.