Check online pricing here:
2Ah two pack:
4Ah two pack:

In this video, John looks at the 2Ah and 4Ah batteries from Craftsman and answers the question of which battery is best for your job.. and why!

This CRAFTSMAN V20 20V max* 4Ah high capacity Lithium battery pack provides up to 3x longer runtime of a standard V20 20V max** Lithium battery. They are compatible with the CRAFTSMAN V20 20V max* cordless power tool and outdoor tool lineup. The premium grade high Performance cells provide high power and long cycle life. This battery is equipped with a 3-LED state of charge indicator for immediate battery charge feedback. No memory and low self-discharge means this battery is ready when you are.

Which Craftsman Battery Should I Get? 2.0Ah vs 4.0Ah Lithium Ion V20 Max Cordless Tool Batteries