They are made of durable ABS plastic and are lined with cork
This Heathrow 50 Place Microscope Slide Box has a unique design and secure clasp. Their lids lock for security and can be completely removed for writing sample information. The 50 slide capacity offers plenty of room. A cork lining provides cushioning. Stacking feet stabilize the boxes. They are constructed of durable ABS plastic. The 8 1/4L x 3 1/4W x 1 1/4H" size fits in the company’s large acrylic slide box organizer.