This is a trapezoidal neodymium magnet, which is a custom-made magnet. The black surface is black epoxy coating, which is more suitable for harsh environments. The performance can be selected from N35-N52, 35M-50M, 35H-48H, 35SH-48SH, 35UH-48UH , 35EH-48EH, the size can be large optional, determined by your application...