For the M12 lineup, you've got 6 choices in batteries. Most of the kits come with either XC4.0 or CP2.0 and sometimes CP1.5.  The CP series, as the name implies, is a compact M12 battery and the one you'll find in a lot of the M12 kits. It's a great battery overall and provides plenty of capacity and run time for most of the M12 tools. I have one for all of my M12 tools in my cabinet. The XC3.0 has the option of a two-pack. Options - Milwaukee M12™ REDLITHIUM™ CP2.0 Battery (48-11-2420) - Milwaukee M12™ REDLITHIUM™ CP3.0 Battery (48-11-2430) - Milwaukee M12™ REDLITHIUM™ CX3.0 Battery (48-11-2402) - Milwaukee M12™ REDLITHIUM™ XC3.0 Battery 2-Pack (48-11-2412) - Milwaukee M12™ REDLITHIUM™ XC4.0 Battery (48-11-2440) - Milwaukee M12™ REDLITHIUM™ XC6.0 Battery (48-11-2460) FAQ & Support Milwaukee Tools do not qualify for 10% Hex Plus discounts. However, Milwaukee does qualify for Hex Plus free shipping. ***ALL SALES ARE FINAL ON DISCONTINUED ITEMS, NO RETURNS