Wonder no more. I had a 1:1 W2DU "beam balun" on my tribander that I just finished taking down the other day. The connection points were looking bad so I decided that since I was rebuilding the antenna to last another year why not do everything including the balun.I bought this balun probably about 18 years ago or so and have heard that some companies are cutting short making them and using ferrite beads inside that are less than ideal. I have also heard that some of these W2DU baluns use a ferrite core which is OK but prone to overload with high power. Being the curious person I am (OK nosey then) I took mine apart to see what it was made of. Much to my surprise and delight I found that I had one of the very good original W2DU baluns as originally designed by Walter Maxwell himself,W2DU.It is not a cheap knock-off that is fairley common these days. It is a 1:1 air core balun wound with 14 gauge wire for high power handling without saturation of the core as will happen with a ferrite core. The first picture is of the unopened balun minus the attachment points to the antenna.You can see where the antenna connection points are on the side. The connection on the top is simply to hang the balun from something and is not connected to anything inside. I should note that this balun is used on a balanced antenna like a dipole or on some antennas that have a balanced feed like my A3 tribander that has a split driven element. The second picture is of the insides of the 1:1 balun. Nicely made and still looking good after almost 20 years outdoors. The coax connects to the left side and the balanced output goes to the connections on the right. Lastly is the rebuild balun with new stainless hardware and tinned copper braid ready for attachment to the antenna. I left the leads long and will trim to length when the antenna is put up. I will install another set of ring terminals and use stainless hardware to attach it to the driver element.