Something like this: http://shop.sdp-si.com/catalog/?cid=p593 http://shop.sdp-si.com/catalog/?cid=p593 So you can decide on a module/PA, buy a few diameters th

Something like this: http://shop.sdp-si.com/catalog/?cid=p593 http://shop.sdp-si.com/catalog/?cid=p593 So you can decide on a module/PA, buy a few diameters then cut off the required face width you need and machine the bore as needed.