One of the most costly items on your classic car is the paint job so you should do every thing you can to protect it.and a good flexible U channel rubber edge trim on the rim of tail light assembly where applicable is a very good investment. Most important is picking the correct rubber edge trim extrusion opening for your application. Most chrome on tail light assemblies is between 1/16 to 1/8 thick. So first determine the chrome thickness using a micrometer I also recommend that you use the metric system as it is simpler and more exact. As most of our edge trim openings are in fractions of an inch here are the conversions to metric 1/16=1.587m, 5/64=1.984m, 3/32=2.381m, 7/64=2.788m, 1/8=3.175. Next pick an edge trim extrusion that has a flat end as it will seal better and always leave the joint where the 2 ends meet at the bottom of the assembly so that moisture drops off instead of seep in. It is also very important to have a good moisture seal as any moisture that gets in around the bulb assembly can lead to trouble. Edge trim sold by the foot is also important why buy 10 feet if all you need is 5 or 6 feet