SBA Communications owns a portfolio of about 46,000 wireless towers throughout North America, South America, and Africa. It leases space on its towers to wireless service providers, who install equipment to support their wireless networks. The company has a very concentrated customer base, with most revenue in each market generated by the top three or four mobile carriers. It owns more than 17,000 towers in the US, which account for about 70% of leasing revenue. Internationally, SBA’s largest markets are Brazil and Guatemala, where it owns roughly 12,000 and 5,000 towers, respectively. SBA operates as a real estate investment trust.