Others say...

"Great M2 stick"
4 Gigs is a great size for holding all the information you need on your phone. If you are looking for this kind of product, this is a fairly simple answer to your needs. Memory size is sure to grow, so the only thing to pay attention to is that there are a couple different physical sizes for memory sticks and if you put the wrong one in it can get stuck.

"Works on W580i"
Works with no problems on both of my Sony Ericcson W580i's. Hard to find anywhere else at time of my purchase.

"SanDisk 4GB M2"
Great product, great price & great shipping. Works like a charm on my W580i. Though Sony says the phone cannot "see" more than 2GB, my phone seems to recognize its a 4GB card. This with any Sony phone makes any Iphone & its price tag look bad.

"I wouldn't know"
well...I'd love to say that it's a great product, HOWEVER...."Digital Media Source" the vendor I purchased it from shipped me the incorrect item, and then refused to work with me at all to rectify the situation. They, in fact, shipped me a cheaper item. I received a usb thumb drive...I ordered a card for my camera. Attempts to contact the vendor were only possible via e-mail. Attempts to obtain a phone number to call, or to have a call placed to me were futile. The 2 e-mail responses I received were 2 words long, and completely unhelpful. Repeated attempts at e-mailing this vendor were simply ignored. I finally resorted to an ugly e-mail referring to the vendor's possible body fat percentage, and propensity for messily eating potato chips on his mothers couch in the basement out of sheer frustration. I will NEVER order anything from them, or ANY Amazon affiliate again. Thank you Digital Media Source and Amazon. You have successfully narrowed the scope of any online shopping I may do in the future, making it possible to quickly weed out vendors that might be out to screw me (or you, consumer).

"works as advertised"
Took it out of the pack and added to my SE W580i.
Added Music, Photographs and was ready to go...