These are the same high-quality inner sleeves used by Mobile Fidelity Sound Lab for their vinyl releases. They are imported, three-ply, anti-static, premium sleeves (similar to rice paper). Back construction consists of a paper layer sandwiched between two sheets of high-density polyethylene (HDPE) with a translucent HDPE front.
Your records are irreplaceable - these sleeves will guarantee they last a lifetime.