Air Tensioners

Have been looking for the "parts list" for making air tensioner for small square baler.  I've gone back through a lot of topics on here and a lot of Google searching.  

 

Pretty much know how to set it up, but not sure of what air bags to get.  

 

Appreciate something from the el cheapo collection available online, really don't want a salvage yard trip with the cold and snow   

 

Thanks,

Shelia

Air Tensioners