Wabco brake booster for the 406, 416, 419, SEE, etc. If your cylinder bore is pitted, your repair kit is not going to work for very long. If you have a smooth bore, then the rebuild kit may be a viable option. The rebuild kit is part #000 586 5843 and available from EI as well.
OEM Surplus Part as New. Wabco. Same part as delivered in the MB Box, just a whole lot cheaper.