1 custom made box protector for many, but NOT ALL,  Steelbooks with Lenticular slipcovers. These were made to fit the top and bottom feeders that don't have booklets.   Please check the size of your Steelbook to make sure it will fit. 

6 7/8 x 5 9/16 x 3/4 or roughly 17.4 x 14.1 x 1.9cm. 

Fully enclosed

Removable Peel Film

Acid free 14mil PET plastic