Mach Sakai reviews a used Tokyo Marui Hi-Capa 5.1 race gun custom with a C-MORE optic from Frontier. He details its many custom features, including its modified barrel, sights, and lightweight trigger, before showcasing its performance through various tests. He highlights the gun's smooth slide movement, efficient gas consumption, and consistent muzzle velocity, concluding that its quick response and light trigger pull make it ideal for speed shooting.