By the way, the number of tunes you can put on a player depends also on their bit rate.
A 128 kbps MP3 file (the lowest bit rate recommended by most users) takes up less card space than higher bit rate MP3s (like 160, 192, 320, etc.) therefore, you can fit more tunes on the same card or player. Some users claim you can use even a lower bit rate like 96, or 80 or 64 kbps on these little players without sacrificing quality. I don't agree, but you'll have to try it yourself. Very subjective what you'll live with.