Great online replacement for lost or broken CS50 batteries. Watch the fragile upper extension, that's why only 4 stars.
These little guys tend to get lost but are a marvel of Lithium ion battery miniaturization. Be careful as the top plastic extension is fragile and tends to break off easily, although this does not affect performance or recharge fit as the magnet does all the attachment. If you have a CS50 you know this well, and Amazon is a great place to get a Prime instant replacement.
Rating: 4 stars