The Pneumatic we used on our Gearbox this year is a 3/8 throw, 9/16 bore Bimba Flat-I cylinder. On their website they have a function where you can select the specifications of the pneumatic you want and it will generate a pdf drawing or 3D model of the cylinder you specified.
Here is the link to the Flat-I configure page
http://www.bimba.com/Products-and-Ca...file/Flat-One/