Many options and opinions
Hi Jerry -You're lucky most or all of the finish is gone. You'll need to sand grey away and go from there. The most popular options or traditional varnish and Cetol. There are many others, like Honet Teak, Bristol Finish, Seafin Teak Oil, etc. I think it's safe to say varnish looks the best but requires the most initial work and ongoing maintenance. I've been somewhat happy with Cetol (looks 80% as good for 20% as much work in my opinion). It has an orangish hue to it that some people find objectionable, but you can get Light and cover with Gloss for a better look. Much more forgiving than varnish.Just a few thoughts.Trevor