American Tower is a holding company. Through its subsidiaries, the company is a real estate investment trusts and an independent owner, operator and developer of multitenant communications real estate. The company's primary business is the leasing of space on communications sites to wireless service providers, radio and television broadcast companies, wireless data providers, government agencies and municipalities and tenants in a number of other industries. The company also provides tower-related services, including site acquisition, zoning and permitting and structural analysis, which primarily support the company's site leasing business, including the addition of new tenants and equipment on its sites.

Crown Castle International is a holding company. Through its subsidiaries, the company owns, operates and leases shared communications infrastructure that is geographically dispersed throughout the U.S., including towers and other structures, such as rooftops (collectively, towers), and fiber primarily supporting small cell networks (small cells) and fiber solutions. The company's towers, fiber and small cells assets are collectively referred to herein as communications infrastructure. The company's core business is providing access, including space or capacity, to its shared communications infrastructure via long-term contracts in various forms, including lease, license, sublease and service agreements.

SBA Communications is a holding company. Through its subsidiaries, the company is an owner and operator of wireless communications infrastructure, including tower structures, rooftops, and other structures that support antennas used for wireless communications. The company's operations are in the U.S. and its territories. In its site leasing business, the company leases antenna space to wireless service providers on towers that the company owns or operates and manages rooftop and tower sites for property owners under various contractual arrangements. In its site development business, the company assists wireless service providers in developing and maintaining their own wireless service networks.