This is for 1:4 scale Mercedes DIII engine from WWI. If you are building Mercedes DIII engine you will need one for right side and one for left side of engine. (Left and right magnetos are little bit different.)
About cleaning the item, read shapeway tutorial for more information, but here comes important part of it:The easiest way to de-grease the models is to submerge them into a mild solution of hot water and dish soap. The water temperature should be around 70ºC/158ºF. Let the parts soak for a couple of hours, the water may turn cloudy as wax and oil separate from your models - you can repeat this process without harming your parts if necessary. You can also use an ultrasonic cleaning machine, or dip the models in acetone for about 5 minutes - if you choose to try acetone, make sure to clean the model thoroughly when you're done soaking.
When the model is ready to paint, it will be uniformly white and should no longer feel greasy.