The wall thickness of a 5-gallon PET preform directly affects its capacity. Designers must determine the proper wall thickness to withstand the internal pressure exerted by the liquid while maintaining the desired volume. Balanced thickness is critical to ensure the structural integrity of the preform, preventing deformation or failure during handling and use.

Neck Design: The neck design of the 5-gallon PET preform is critical to the capacity and compatibility of the cap. Designers must ensure that neck dimensions and thread specifications are compatible with standard closure and dispensing mechanisms. Additionally, the neck design should facilitate filling and pouring while ensuring a secure seal against leakage or contamination.

Handle Design (if applicable): In some cases, 5-gallon PET preforms may have handles to facilitate handling and transportation. Designers need to consider the size, shape, and location of the handle to ensure it complements the capacity of the preform. The handle design should provide ergonomic comfort, sufficient grip, and structural integrity to support the weight of the preform when filled with fluid.