These may be the ideal sleeves balancing clarity, cost, and strength. 

Polypropylene LP sleeves for 12" records. Completely transparent to show off your artwork while keeping your LPs safe. 

324 mm x 324mm (12.75" x 12.75" x 1.5" flap). 

Made from 75 micron (3 mil) clear polypropylene.

100 sleeves included per pack. Unbranded packaging.