okay, I'll answer. I use a one inch needle and go straight in....perpendicular to the hide. One must be sure to only inject into the triangle area of the neck which is well behind the poll and in front of the shoulder blades. If you were to see a skeleton of the cow you will notice that the neck vertebrae at the " triangle area" is down in the lower part of the neck and is very close to teh surface near the poll. The big thing is really making sure that you have good restraint system because cattle "hate" neck shots and tend to fling, lurch, and leap if able.