Genuine Blue 10 ml Glass Roller Bottles with Stainless Roller Ball; Set of Six Roll-on Bottles with One Extra Roller; Ultra-Premium Thick Glass with Small Lids that Seal Tightly Stainless steel roller ball glides on seamlessly and effortlessly. The blue glass protects your precious oils or perfumes from harmful UV rays. Extra roller just in case you need or ever lose. We cannot guarantee it will fit other rollers but MAY fit in other 10 ml roller bottles :). Extra tight fitting lids. Ball will stay in tact regardless of oils used. This is different from plastic which may deteriorate with use.