Aluminum Bottle Caps

About

These aluminum bottle caps are built for product makers who want a clean, premium-looking closure without the guesswork. Available in black and silver finishes, they're PE-lined aluminum screw caps sized from 18-400 up to 33-400 — fitting Boston round glass bottles from 0.5 oz all the way through 16 oz. If you're running a product line with multiple sizes, you can stay consistent across every format. Browse by neck finish: glass bottles that pair with these caps are available throughout the store, and all caps ship wholesale in box quantities of 600 units per size. Black aluminum caps and silver aluminum caps are both stocked — pick the finish that fits your brand. What Are Aluminum Bottle Caps Used For? Aluminum screw caps show up across a wide range of product categories because they hit a rare combination: they look expensive, weigh almost nothing, and hold up in shipping. The most common uses are cosmetics and skincare (serums, facial oils, toners), essential oil blends, tinctures, aromatherapy products, and any liquid formulation that benefits from a clean, professional finish. They're also popular with brands building private label lines where the packaging has to look retail-ready from day one — a matte black aluminum cap on a frosted Boston round reads premium in a way that a plastic cap simply doesn't. Understanding Neck Finish Sizes Every cap in this collection is labeled with a neck finish designation like 18-400, 20-400, 24-400, or 28-400. The first number is the diameter of the bottle opening in millimeters. The second number (always 400 here) refers to the thread style — it's a continuous thread, meaning the cap screws on and off smoothly in one motion. Match the cap's neck finish to your bottle's neck finish and you'll have a secure, leak-resistant seal. If you're not sure which size your bottles take, check the product listing for your bottle — the neck finish is listed in the specs. Why Aluminum Over Plastic? Plastic caps work fine for plenty of app