Apple has added an 8GB model to its range of red iPods benefiting Aids research.

The 8GB model joins the 4GB iPod nano as part of Apple's contribution to the Product Red programme founded by U2 singer Bono and philanthropist Bobby Shriver.

Product Red raises money for the Global Fund to Fight Aids, Tuberculosis and Malaria in Africa. Other retailers participating in the program include Gap, Converse and American Express. 

Apple donates $10 from each of the red iPods to help Aids research in Africa.

The 4GB and 8GB models offer the same features and price tag as Apple's other second-generation iPod nano models introduced in September.

The 4GB red iPods were released in mid-October, and Apple said that it is pleased with the results of the campaign.

"Customer response to the red iPod nano has been off the charts," said Greg J oswiak, vice president of worldwide iPod product marketing at Apple.