Fits bottles with an 11 mm (0.425 inch) neck opening - standard on most 5 ml and 15 ml bottles from doTERRA, Young Living, Plant Therapy, Rocky Mountain, Mountain Rose, and Revive 10ml bottles. Please measure before ordering - place a ruler across the bottle opening and check for 11 mm (inside edge to inside edge). Leak-proof 3-part design with rust-resistant stainless steel ball for smooth, even application. Ideal for thicker oils or blends made with fractionated coconut oil. Glass rollers available for thinner oils. Durable black collar holds the ball securely; collar can be removed for cleaning and re-use. Includes 12 stainless steel roller inserts and 12 matching black caps. Product Description: After retiring from the military, we started a small essential oil supply business in South Carolina dedicated to quality bottles, caps, and roller tops. We redesigned our products to last longer, fit better, and keep your valuable oils safe. Important Fit Tip: These stainless steel roller tops are designed for bottles with an 11 mm (0.425 inch) neck opening. This size is standard for most 5 ml and 15 ml bottles from doTERRA, Young Living, and other major brands listed above. To check, place a ruler across the opening of your bottle and measure from the inside edge to the opposite inside edge. If your opening is not 11 mm, these rollers will not fit. The rust-resistant stainless steel ball glides smoothly for consistent application, while the 3-part leak-proof design keeps your oils secure. The black collar holds the ball firmly in place, can be removed for cleaning, and allows reuse with different blends. Best Use: Stainless steel rollers are ideal for thicker viscosity oils or blends that use fractionated coconut oil. For thinner oils, perfumes, or light blends, we also offer glass roller tops. Each set contains 12 stainless steel roller inserts and 12 black caps.