Briley makes a diffusion choke that I purchased about 8 years ago at a national trapshooting competition. I baught (2) one was for my remington 870, the other for my mossberg 500. Both shoot well with lightfeilds and winchester partition golds. The mossberg also shoots brenneke and winchester rackmaster slugs well but my 870 doesn't like them. But then again my 870 has always been picky, even when i shot with ic and modified cylinders. It only prefered one slug type over all the rest and shot very well with it. The brenneke and rackmaster style slugs have prettymuch the same idea, they are designed to be able to shoot out of a smooth or rifled barrel. I will try to post some picks of both the mossberg rifled choke and the choke for the 870. hope this helps, if I can locate the gentleman's card, I will be glad to email you and send you his info. Both of these chokes have proven well for me in both of my shotguns.