You can lap it your self.
It means to flatten the head.
Use a pice of glass or polished stone or a table saw top. It just needs to be a flat surface. Use sand paper to surface the matting surface of the head and remove any high or low areas whichever way you want to look at it. I usually start with 400 grit wet dry and use soap and water or windex as a lubricant. If there are any big differences then you can use 220 to get the bulk removed and finish with 400 until it dead flat. The idea behind this is over time the can warp. You may find your has not but you always want to check to be sure.
It means to flatten the head.
Use a pice of glass or polished stone or a table saw top. It just needs to be a flat surface. Use sand paper to surface the matting surface of the head and remove any high or low areas whichever way you want to look at it. I usually start with 400 grit wet dry and use soap and water or windex as a lubricant. If there are any big differences then you can use 220 to get the bulk removed and finish with 400 until it dead flat. The idea behind this is over time the can warp. You may find your has not but you always want to check to be sure.