Following a successful trial on the demonstrator unit SMB136C, SMRT Buses purchased a further 50 units of the Citaro (Mk II or facelift version) in two batches. On 21 March 2011, these production batch buses began their debut on services 75, 531, 920 and RWS8 Staff.

The modular nature of the Citaro meant that production orders for both SBS Transit and SMRT Buses were rolled out from the same factory and to a degree share common features, such as the bodywork and the driver's dashboard. These buses utilize BlueTec 5, the selective catalytic reduction (SCR) technology by Mercedes-Benz requiring the use of AdBlue, to meet the Euro V emission standards.

Changes to the production batch Citaros are mainly aesthetic and the automatic transmission used - the production units were fitted with Lawo BENEFIT EDS (notably with route details on the side EDS), seat covers in its corporate livery and swing-out doors. SMRT Buses retained its option of the OM906hLA engine (6,374cc) and uses the new generation ZF EcoLife 6AP 1200B (6-speed automatic) gearbox for Batch One, but matched up with SBS Transit's choice of Voith D854.5 (4-speed automatic) transmission for Batch Two buses. The interior is fully low-floor and its air-conditioning was supplied by Konvekta. Both operators have also customized their interior fixtures to a certain extent in order to blend in with their existing WAB fleet.