None of the reviews I read mentioned the weight of this product. My Wifi iPad Mini weighs 11 oz. This product is composed of three separate sections. The plastic section that covers the iPad weighs 4 oz, the rubber portion that partially covers the plastic section weighs 3.1 oz, so with these two parts on the iPad you have 7.1 oz in addition to the 11 oz weight of the iPad for a total of 18.1 oz. The other section, which is used to protect the iPad while traveling and as a base to support the iPad in two different upright positions, weighs 4.3 oz.
This product is well constructed, fits the iPad Mini well and should provide good protection. The other reviews covered other aspects of the product so I won't cover those. I gave this five stars because I concluded that it should protect the iPad from most accidents, which is the main purpose. As to the additional weight, any case built to protect the product will have a weight penalty. So the choice is protection with a weight penalty or less protection without the case.