It's normally good form to introduce yourself and say hello to the forum before you get into the asking questions phase!.
It's 28.5mm , same as most all Seiko full size auto divers. 4r15/6, 7s25/6, 7s35/6, 4r35/6, 6r15 all use the same dial feet and are predominantly interchangeable with like for like crown position.
A strong note of caution!! the SRP043 is one of only a handful of Seiko 7s based watches that is a true 4 o'clock crown - NOT 3:18!!
The forum search function shows http://www.thewatchsite.com/21-japa.../38209-potential-mod-my-spork.html#post265712