Anyone know the size or where to order these. I think they are metal eyelets, but i could be wrong. I ask because I am planning on undertaking a new venture and start making slide racks. With the inserts I can cut down production time and offer the racks in some standard designs. I will also be offering female glass joints for slide to rest in, but that will be on a custom basis as the joints are pricey. Here are the first two I have done, both customs.