Is a 26-inch chain too long for a man?

It depends on neck size and how you wear it. On most men 26 inches falls at or just below the collarbone, good over a shirt; for a close-to-the-neck look, 20 to 22 inches is more typical.

Will the stainless steel tarnish or turn my skin green?

Solid stainless steel does not tarnish like plated brass and does not leave green marks the way copper alloys can. It may dull slightly with sweat and soap, which a soft cloth cleans off.

Can I shower or swim in it?

Yes. Stainless steel handles water, sweat and soap well. Chlorine and salt water can dull the finish over time, so rinse and dry it after pool or ocean use.

How wide is a 4mm curb chain?

About the width of a standard pencil lead bundle, roughly 4mm across each link. It is noticeable but not chunky, and it fits most pendants with a bail wide enough to slide on.

What is included with the necklace?

The listing shows the chain itself. Check the product page for whether a pouch or box comes with it if you plan to give it as a gift.

How has the chain held up after a week of wear?

One owner reported on the chain after a week of ownership. That is a short window, so judge long-term tarnish and clasp wear from longer-term owner reports.