Introduction
"Lean synchronization is the aim of achieving a flow of products and services that always delivers exactly what customers want, in exact quantity, exactly when needed, exactly where required, and at the lowest possible cost. It is a term that almost synonymous with terms such as 'just-in-time' (JIT) and 'lean operations principles'. The central idea is that if terms flow smoothly, uninterrupted by delay in inventories, not only is throughput time reduce, but the negative effects of in-process inventory are avoided. (Slack, Johnston, Betts & Chambers, 2009)" Womack and Jones (1996) states that Lean Thinking is within the five core principles behind the Toyota Production System, and come to be the most efficient in the world today. Principles of Lean or the Toyota Production System are continue to be of great interest to the operations community. Lean principles supply an incentive for manufacturing companies to imitate, and it always in their improvement program. Therefore, Lean Thinking is a way of managing an organisation to improve the productivity, efficiency and quality of its products or services. I will use some literature review to show how the key principles of lean can help improve sustainsble supply chain efficiency. On the other hand, I will show argument about lean principles.

Five principles of lean
The first principle is specify what creates value from the customer perspective. It means to creates value for customers, such as, product and service, and it will supply more good product and service for the customer. Bicheno and Elliot (1997) defined that " value analysis is concerned with challenging in the value of existing and often well-established products and services, with a view to improving them. Evans and Collier (2007) show the supply chain can use the electronic transaction capability to know the changes in demand and supply immediately, and it good to eliminate parts of the traditional value chain structure and streamline operations. Therefore, the electronic transaction capability as add value for customer service, it let the supply chain become shorter and delivery the product more quickly than before. Besides it, Evans and Collier (2007) also explain value chain is more efficient and create value for their customers.

The second principle is identify steps across the whole value stream.
Womack and Jones (1996) states the value stream is the raw materials along with knowledge and information enter into the system upstream. Evans and Collier (2007) state value stream maps might include some information about machine uptime and reliability, process capacity and the size of batches moving through the process. Evans and Collier (2007) also illustrate that if the value stream is faster than the takt time, it generally means that waste in the form of overproduction is occurring; when it is less, the firm cannot meet customer demand. Taylor and Brunt (2001) explain that value stream needs the key staff involved in the planing and production of these two products, included material purchasers, production controllers, shop floor staff from each of main processes, warehouse staff, transport staff, and the company Logistics Manager. According to the planing every step, it can help to reduce the waste. The next, Taylor and Brunt (2001) explain that use the suite of Value Stream Mapping Tools can quantify the processes and analyse the waste.

The third principle is make those actions that create smooth flow
Evans and Collier (2007) states that " Continuous flow processes, by their very nature, are highly efficient because materials move through operations without stopping. Lean operating system seek to apply the principles of continuous flow to the production of discrete parts by reducing batch sizes, ideally to a size of one-that is, using single-piece flow." It is good for company to match production to customer demand. "Stabilized production flow, in lean production, work-in-progress