These are NEW replacement batteries for Garmin Forerunner 405s, 410s and others too...ePluse2  To fit in the Abacus you just pull off the tabs (so I am told).

You can find instructions for replacement on youTube: How to

 Specs: 3.6V 300mAh  30.5*5.5mm RoHS compliant

Expect the same performance from this battery as when your watch was new.  See your owner's manual page 40.  The stock battery lasts 3-5 hours in Training Mode, 8 hours with the "GPS on" and a week in "time only mode."

*****ATTENTION*****

If you are not comfortable performing the work, see my other items where I provide the installation service using EXTENDED batteries at a very reasonable price. Why risk damaging your watch, when I can do it cheap and fast!  

I highly recommend this 350mAh extended installation only available from me.  You will enjoy your watch much more. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190674467062&ssPageName=STRK:MESE:IT#ht_513wt_932