Ballistic (http://www.goballisticcase.com) has unveiled the Ballistic SG (Shell Gel) for the iPhone 4. It’s an US$29.99 solution for customers who desire a slimmer form factor but also need durability, according to the folks at Ballistic.

It has a soft, outer TPU for shock absorption and an impact resistant polycarbonate middle layer. On the outside is a soft silicon layer with ballistic corners to absorb the shock of a drop.