Organisations keen on quality IT service delivery but lacking or not wishing to invest in the necessary expertise often outsource this specialised field to an expert which provides the technology, guidance and recommendations, support and maintenance required. This is a Managed Services engagement, with the vendor known as Managed Services Provider or MSP. In the Managed Services model, a subscription is usually paid making the service fixed cost, distinct from the break/fix model where the service provider bills only for work done. The MSP model incentivizes preventative maintenance and is especially popular for mid-sized organisations.