Slim TPU Rubber Flexible Soft Case Shockproof Phone Cover For Alcatel Idol 4S.
$1.61 with free shipping at eBay.
The Alcatel Idol 4S is glass, front and back, and a shockproof case is a really good idea to help protect the phone.
I've bought a few different cases for the Idol 4S, and most don't do the trick as they fail to cover the corners of the screen offering no protection at certain points of impact.
THESE incredibly affordable cases overlap the entire edge of the screen, protecting the edges and corners. They're far better than cases I have bought for 10x the price.
If you recently bought an Alcatel Idol 4S mentioned on other threads here at Slickdeals, I would highy recommend this purchase.
Currently available in several colors: clear, black, blue, pink, and purple.
I have bought several from this eBay merchant. They're shipped promptly. 10% off the second if you buy two.