When converting your parking lot lighting to either LED lighting or just adding more lights and making them adjustable, you will need to add parts to your light poles such a bull horns and or tenon tops. When changing the layout of your parking lot, you must start at the pole. Does it have a tenon or just an open top pole, this will give you a starting place to start your lighting rebuild. If you have a round tenon on the top of the pole you are in great shape, simply verify the outside diameter of the tenon top, select the bull horn, spoke adapter or upsweep arm stlye that fits your plan. As just a suggestion, for square poles or square tapered poles most people prefer the square style bull horns. When using round or round tapered poles the selections are usually the spoke adapters or the upsweep style arms. You can mix square poles with round bull horns or round poles with square bull horns. It is really about the look and preformance you are looking to obtain.