Hard gelatin capsule shells consist of two prefabricated cylindrical parts (a cap and a body), each with a circular closed end and an open end. The body is slightly smaller in diameter than the lid and fits inside the lid.

Hard gelatin capsule shells are manufactured by shell suppliers and supplied to the pharmaceutical industry as empty shells, which are then filled in a separate operation. During the operation of the capsule filling unit, the body is filled with the drug substance and the shell is closed by bringing the body and lid together. Hard gelatin capsule shells consist primarily of gelatin. In addition to gelatin, it may also contain substances such as plasticizers, colorants, opacifiers, and preservatives, which can encapsulate or improve its properties. Hard gelatin capsules also contain 12-16% water, but water content may vary depending on storage conditions.

Empty hard gelatin capsule shells come in a variety of sizes, any number from 000 to 5, where 000 is the largest size and 5 is the smallest size. Apart from the development of self-locking capsules when automatic filling and packaging machines were introduced in the 1960s, the shape has changed little since its invention.

The size of the hard gelatin capsules chosen is determined by the requirements of the formulation, including the dosage of the active ingredient and the density and compaction characteristics of the drug and other ingredients. The first step in estimating the optimal capsule size for a given product is to use the tap density of the powder and the bulk density of the pills, micro tablets, and granules to determine the density of the formulation. The measured formulation density, target fill weight, and capsule volume can then be used to calculate the appropriate capsule size. The fill weight of the liquid is calculated by multiplying the specific gravity of the liquid by the volume of the capsule body multiplied by 0.9.

Some intermediate sizes ("extended sizes") are produced for special needs. These capsule sizes typically have an additional 10% fill compared to standard sizes such as Extra 00 Capsule (00el), Extra 0 Capsule (0el), Extra 1 Capsule (1el), Extra 2 Capsule (2el) Wait.

Xinchang Hexin Capsules Co., Ltd. is an Empty Gel Capsules Manufacturer and Clear Vegetarian Capsules Supplier in China. It produces and sells Quick Dissolving Capsules, Empty Gelatin Capsules, and other empty capsules all year round.