The oil rollers are filled with natural crystal chips. You can open it from the top and put the oil inside.
Crystal chips available:
Clear Quartz, Rose Quartz, Amethyst, Black Obsidian, Red Jasper, Fluorite, Lapis, Sodalite, Aventurine, Tiger's Eye
Size:
Dimeter - 2.0 cm
Heigjt - 8.5 cm