They are very easy to fit. The bottles need to have a 28mm o/d screw with at least 2 rows of pitch to the thread.
eBay
Vacuum bottle cap thermos bottle stopper thermos bottle cap outdoor travel cup bottle cap for thermos cup outlet bottle cap
Aliexpress UK
Made from high quality HDPE (High Density Polyethylene). Food safe Commonly used for many household chemicals and detergents, oils, toiletries, health and beauty, confectionery and general food products.
eBay
Vacuum bottle cap thermos bottle stopper thermos bottle cap outdoor travel cup bottle cap for thermos cup outlet bottle cap
Aliexpress UK
Too be used with a Crown Capping Tool.
eBay
20pcs Circular Plastic Bottle Cap Reusable Multi-purpose Drinking Bottle Cap with Gasket 28mm Screw Bottle Cap
Aliexpress UK
Color: As Picture Shown. Due to light and monitors effect, color difference may exist slightly. There are NO EXCEPTIONS!
eBay
1pc-automatic opening and closing bottle cap, oil nozzle, oil bottle cap, soy sauce bottle head, oil nozzle, opening bottle mout
Aliexpress UK
Add the perfect touch to your home brew beer bottles with these Crown Caps. Made of high-quality metal, they come in packs of X25, X50, X100, and X250. These caps are designed to fit snugly on your bottles and provide a sleek finish to your brew. Ideal for beer enthusiasts, these Crown Caps are perfect for adding a professional touch to your home brew. They are easy to use and will give your beer bottles a polished look. Whether you are a beginner or an experienced brewer, these caps are a must-have for any beer lover. Get yours today and take your beer to the next level!
eBay
10 Pcs Diameter 18/20/ 24MM Plastic Bottle Cap Replacement Flap Cover For Lotion/Toner Bottle Cosmetic Bottle Cap Accessories
Aliexpress UK
Used for capping the bottles with their own beer, juice or liqueur health.
eBay
Multiple Size Water Bottle Cap 4.5cm/5.2cm Vacuum Flask Lid Thermos Bottle Cap Stopper Travel Cup Replacement Cover Thermos Cup
Aliexpress UK
Bottle Capper With Twin Lever. Used for capping the bottles with their own beer, juice or liqueur health.
eBay
6/2/1PC Food Grade Silicone Bottle Cap Wine Stopper Oil Vinegar Leak Proof Stopper Wine Champagne Bottle Caps Barware Bar Tool
Aliexpress UK
Capacity: 500ml. Colour - Amber.
eBay
4.5cm/5.2cm Vacuum Flask Lid Thermos Bottle Cap Stopper Travel Cup Replacement Cover for Thermos Cup Export Bottle Cap Black
Aliexpress UK