Efluky by Amazon offers Prime members its Efluky 18-volt 3Ah Nickel-Cadmium Cordless Tool Battery 2-Pack for Ryobi for $31.99 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $7.99.) That's $7 under our mention from two weeks ago, $78 off, and the lowest total price we could find. They're compatible with tools that require Ryobi ONE+ P100 P101 batteries. Deal ends December 20.