This guide covers standard box sizes across every major industry, explains the difference between internal and external dimensions, breaks down carrier-specific size requirements for USPS, UPS, and FedEx, and gives you practical tips to find the right fit for any product. This document provides specifications for various types of plastic distribution boxes, including their dimensions and features. It describes HA, HK, and LGD series boxes with dimensions ranging from 100-415mm in length, 105-323mm in width, and 75-140mm in height. Actual units use PNP status indicator, NPN status indicator, or neither. Dimensions are shown in mm (in.