What shape are connectors typically labeled as in duct systems?

In duct systems, connectors are typically labeled as circular. This labeling is commonly used because circular ducts and their connectors provide a uniform airflow and are efficient at minimizing resistance as air moves through the system. This shape helps to maintain a consistent flow across the cross-section, which is beneficial for both airflow and energy efficiency. Additionally, circular connectors easily accommodate variations in duct sizes and are widely recognized in both residential and commercial applications, leading to their prevalence in design and documentation.

The other shapes, while they may be used in specific applications, do not generally represent the standard shape for connectors across most duct systems. Rectangular and square connectors can be used, but they often require more space and create more air turbulence compared to their circular counterparts. Oval ducts can exist, but their use is more niche and doesn't dominate the overall market like circular ducts do. Hence, circular connectors are the most recognized and utilized shape within the context of duct systems.