- Men’s slate blue shirt - Mandarin collar, long buttoned sleeves - EASY-REGULAR fit, pure French linen - Buttons to fasten, IKKS button on left cuff - IKKS #actforbetter: fabric contains pure Masters of Linen® and European Flax® certified flax Love summer. Love shirts. Love linen. The linen shirt in a slate blue colour goes for a mandarin collar, the best combo.