Froukje Zijlstra

Croonwolter&dros BV operates as an engineering company with activities in the industrial, infrastructure, and utility sectors. It offers asset management, automation, geothermal, maintenance, system integration, tunnel design, tunnel maintenance, inspection, safety, revitalizing, and security services. The company was founded by Hendrik Jan Wolter in 1875 and is headquartered in Rotterdam, the Netherlands.

TBI Holdings BV operates as a financial holding company with activities in the engineering, construction and development, and infrastructure industries. Its subsidiaries include Comfort Partners, Croon Elektrotechniek, Eekels Technology, Era Contour, Groothuis Wonen, Hazenberg Bouw, Hevo, J.P. van Eesteren, Koopmans Bouwgroep, MDB, Mobilis, Nico de Bont, Synchroon, Timmermans Infratechniek, Voorbij Funderingstechniek, Voorbij Prefab, Wolter and Dros, and WTH Vloerverwarming. The company was founded in 1981 and is headquartered in Rotterdam, the Netherlands.

De Keizer Marine Engineering BV is an electrical system integrator in the field of super yacht construction. The head office is located in Zaandam, Netherlands, and there are project locations in Makkum, Aalsmeer, Monnickendam, Alblasserdam, Kaag, and Zwijndrecht. The Dutch company realizes projects and carry out maintenance and service work. The private company was declared bankrupt on October 15, 2020, but was relaunched on December 17, 2020, by Eekels, a subsidiary of TBI Holdings. The majority of the employees of De Keizer Marine Engineering kept their jobs after the relaunch. The company was founded in 1965 and has been a family business since then. The CEO of the company is Hendrik de Haan.

Part of Stichting TBI, TBI Bouw BV is a Dutch company that provides engineering and construction services. The company is based in Rotterdam, Netherlands.