Base it on cable/rod diameter, load requirements, and take-up length needed.

Eye & Eye and Jaw & Jaw are the most common; both are available in multiple sizes.

It’s a high-grade alloy containing molybdenum, which resists rust and pitting from saltwater.

316 stainless offers better corrosion resistance, especially in marine and coastal conditions.

A turnbuckle is a rigging device used to adjust tension between two components, often cables or rods.