The "M mark," which is also the logo of Matsuyama Oil and Fat, is embellished with the logo as a sign of gratitude for the 30 years since its launch (on the back and under the neck). Heavyweight (medium-heavy) T-shirt made of 100% cotton, 5.6 Oz. Double-stitched seams around the neck to prevent yawning. The body is cylindrical and the seams do not touch the sides or underarms.