GMT movements are great, they allow you to track multiple time zones with ease. However, this added functionality often comes at a cost—thickness. The additional gears and components required for the GMT function naturally increase the height of the movement, making most GMT-equipped watches bulkier than their standard counterparts. That's why we've engineered the NMK357 SSK Slim Domed Sapphire Crystal specifically to reduce the overall thickness of your Seiko SSK. It is designed to be installed with our SSK Slim Bezels and a sloped bezel insert to give you the slimmest SSK mod possible. Parts Compatibility:Movement: Compatible with NH34/35/36/70/71 etc Crystal Gasket: Compatible with SSK Crystal Gaskets.Bezels and Bezel Inserts: Any SSK Slim Bezel and Sloped SKX007/SRPD Bezel Inserts.