Hello: The diameter is 3/16 inch. I'd recommend Sta-Loks over Norseman - I
think they go together easier. Last time I checked, they are cheaper as
well. Brion Toss Rigging in Port Townsend, Wash has good prices on these,
and is a wealth of help as well, including a video on installation. I
purchased mine (sta-loks and Loos rigging wire) from Cascade Yachts in
Portland, OR at a similiar savings. Using them on both ends doesn't cost
much extra. I agree that you need to make up your rigging to fit your boat,
just make sure to tune the rig first, mark the turnbuckles, then drop the
mast and make up the new rigging to match the old, but adjusting the wire
length, not the overall length, so the turnbuckles are half to two thirds
open with the new rig. Things may have moved around a bit over the years,
and no sense recreating a rig that can't be adjusted properly. Check the
turnbuckles well - I had two cracked ones and replaced the lot. Also, and
Steve Birch will second this, check the stemhead fitting for cracks and
bending. I had mine reinforced, and I know Steve was dismasted some time ago
because this fitting gave way. A toggle at the base of the forestay is a
wise thing. Good luck. Bill Bach, V1071