HandHeldItems offers this Carbon Fiber Back Glass Skin for Apple iPhone 4 in Black (pictured) or White bundled with a $1 HHI Store Credit for $2.99. Coupon code "iphone4backcovers" cuts it to $1.99. With free shipping, that's tied with our mention from last fall and the lowest total price we could find for such a skin by $3.

Of note, also available is the Plate Guard Back Glass Skin for Apple iPhone 4 in Silver Metallic or Gold Metallic bundled with a $1 HHI Store Credit for $2.99 before the coupon above, $1.99 after. With free shipping, that's the lowest total price we could find for such a metallic skin by a buck. Coupon expires May 15.