Napster offers the following audio qualities:
AAC - up to 320kbps
ACC is the standard audio format used by steaming services. AAC files are considerably smaller than Lossless or Master quality and are great if mobile data usage and smaller file sizes are important.
You can select between Efficient (64Kbps), Normal (192Kbps) and High (320Kbps) in the Audio settings.
Lossless - 44.1khz / 16bit
Lossless audio is the same quality as listening to a CD. These tracks are available in FLAC, a lossless format which reduces the size of the files without altering their original quality.