Amazon.com: Stainless Steel Roller Balls & Lids for Standard 5, 10, 15, and 30 ml essential oil vials. (Leak-proof, and fits on your oil bottle) Pack of 6 rollers & 6 lids.
Amazon.com: 12 Stainless Steel Roller Ball Roll On Inserts for Essential Oil Bottles 5ml and 15ml Amber doTERRA and Young Living Bottles : Beauty & Personal Care
Roller Ball Top for Mettler-Toledo™ Parcel Scale H-4653 - Uline
48 FROSTED 5ml PREMIUM Roll On Bottles Stainless Steel Roller Balls 5 – Grand Parfums II