Chiltern Railways operates commuter/regional rail passenger services from its central London terminus at London Marylebone along the M40 corridor to destinations in Buckinghamshire, Oxfordshire and Warwickshire, as well as long-distance services to the West Midlands along two routes. Services on the Chiltern main line run from London Marylebone to Birmingham Snow Hill, Stratford-upon-Avon and Oxford, with some peak-hour services to Kidderminster. Chiltern Railways also runs trains on the London to Aylesbury Line to Aylesbury (with some trains terminating at Aylesbury Vale Parkway instead), on the Princes Risborough to Aylesbury and Oxford to Bicester branch lines. This Procurement also covers East West Railway from Oxford to Bletchley or any other extensions that Chiltern Railways are contracted to operate. Chiltern Railways operates a mixed fleet of rolling stock to fulfil its rail passenger services. The fleet consists of both diesel multiple units (DMUs) and diesel loco hauled Mk5a coach stock. The fleet maintenance plan set out what maintenance tasks are required for the rolling stock and at what maintenance periodicities. The maintenance tasks include changing various fluids and filters to ensure the safe operation and maintain the performance of the fleet. As such Chiltern Railways require one contract to supply these filters to ensure continuity of supply, so that the maintenance tasks are performed at the correct intervals. To protect manufacturer warranties, only the manufacturer´s recommended filters can be used which forms the specifications of this ITT. Only the filter makes and part numbers identified in the specifications are to be supplied and no substitutions will be accepted. Bidders must be capable of supplying all products within the basket of goods that make up the Specifications. No bids will be accepted where a Bidder is not able to supply all the product types that make up the specifications. Chiltern Railways will place orders for the products throughout the term of the agreement so that sufficient inventory levels can be maintained at its maintenance sites accordingly.