50 Anti Static Round Bottom 12" LP Record Album Inner Sleeves HDPE 37.5 Micron Made of the highest quality 37.5 micron HDPE (high-density polyethylene). The Round bottom sleeve is die-cut for a perfect fit over any 12 inch record. Offers resistance to static build up and protects against abrasions. Their distinct curved base will allow you to easily glide an LP into the tightest fitting jackets. Fits directly over record.