The most general screw on size in pharmaceutical is 18-415 and 20-410. 24-410 and 18-410 are also used for big topical spray and glass bottle separately.
The size of closure is defined by “T”-“H”. “T” refers to the length of inner diameter of closure in mm unite. “H” refers to the deepth of closure but the value can not refected by any length. The value of “H” can be obtained by standard table. For example, if inner diameter is 18mm and deepth is 1.5mm (0.59inch), the closure size is 18-415.
To prevent leakage, the closure must fit the bottle neck. There two key points including “T” and “H” must be compatable separately. Acutally, in the bottle’s parameters, no “T” and “H” terms are defined. Here they are indicated just to explain how closure fit the bottle neck.
18-415 and 20-410 are used for plastic bottles. Because oral or food safety spray medicine is filled in small bottle normally, these two sizes are the most often used in pharmaceutical nasal, oral, throat, mouth, ear sprays.
If the screw bottle is a glass bottle, 18-410 will be used. If 18-415, the “H” length can not fit.
Topical spray are often filled in big bottles. Big bottles normally have big neck 24mm. Therefore, 24-410 need be used. Other non-pharmaceutical sprays such as kitchen spray, screen spray use 24-410 normally due to the same reason.