thanks Wayne and thomas I was comparing the sigma 18 and the magnum 18 from the Eminence website as you refer Thomas they look almost identical but as Wayne said in earlier post the magnums have a copper shorthing ring according eminence to mninimize distortion .Here in Mexico Thomas I can get the eminence in very competitive prices the Wayne prices I belive are the best in the States but I must pay besidse shipping customs du ties the only eminence Mexico dealer can get me better prices but buying dealer quantites very tenting .again thanks both