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) and work with both LPs and laser discs. Back construction consists of a paper layer sandwiched between two sheets of high-density polyethylene (HDPE) with a translucent HDPE front. This equals or surpasses the discontinued VRP inner sleeves.
This record creates new possibilities of inspecting and adjusting record players. Most tests (except for frequency response) can also be carried out without measuring instruments, just by listening, and are therefore particularly well-suited for the ambitious music listener who wants to know how well his system deals with demanding signals under realistic conditions, and whether there is a need for repairs or improvements.
Thanks to Albrecht Krieger for his ideas and advice.