You are looking at 1 pack of 50 Semi-Rigid Card Holder Type 1 (50 Count).  These are the well known requisite for PSA grading submission. 

Specifications:

• Perfect for pre-57 sports cards as well as thick memorabilia cards
• Crystal clear
• Made of high-quality, rigid PVC

Exterior Dimensions:

3 5/16 X 4 15/16