In our view, these feeler gauges are the best and most accurate for adjusting the valves on your four valve boxer. When adjusting the valves, it's very important to use two feeler gauges. If you were to adjust one valve at a time, the small amount of play that exists in the rocker arm bearings will make it nearly impossible to get an accurate and consistent adjustment on both valves. The trick is to have two feeler gauges, one for each valve. You'll be able to evenly match the drag that you feel on each set of valves.
Also, for vintage 2-valve BMW, these work great for setting the point gap.
These feeler gauges are the perfect length and each one features a grippy plastic handle that provides the feedback needed for an accurate valve adjustment, even with oily hands.
NOTE: Sold individually.