Decent reviews on Amazon, RRP shows as £14.99 but doubt anybody would pay that. £2.34 + free delivery seems a good price though.
Reviews state this is compatible with both iphone 4 & 4s
Griffin's FlexGrip case wraps your iPhone 4 in durable silicone that's easy to grip and protects against dirt, dings, dents and scratches. Fits snug around your iPhone 4, and allows complete access to audio output jack, dock connector, Multi-Touch display, and all controls.