Staples offers the uNu DX 6 iPhone 6 MFi Battery Case in matte black for $42.99 with in-store pickup, which is more than 46% off retail and the best deal we’ve seen by $6. Shipping will cost you an additional $9.95.
Its 3000mAh battery should provide a boost of up to 125% of extra power. At just 15.9 mm thick, it maintains your iPhone’s slim profile, while still providing protection against bumps and drops. Nearly 400 Amazon reviewers rate it 4.7 out of 5 stars. What’s more, we reviewed this exact model and it has since become one of our favorite iPhone 6 battery cases.