A band without diamonds has nothing to compete with. Your center stone stays the focal point and the metal frames it instead of adding a second line of sparkle. That helps most with a busy engagement ring: a halo, a pave shank or a three stone design already has plenty going on, and a clean band calms the whole hand down.
It works the other way too. A simple solitaire with a bare metal band looks quiet and deliberate, which is the look many women want on a hand they will see every day. If you have not picked the engagement ring yet, browse solitaire settings for women with the band in mind.
Match the width to the shank of your engagement ring, or go a touch narrower. A band much wider than the shank can make the center diamond look smaller, while one close in width makes the pair read as a set. Long fingers carry a broader band easily; on a shorter finger, a slim one leaves more skin showing and looks better balanced.
Comfort counts as well. A wider band covers more of the finger and can feel snug, so take the width into account when you measure; Rare Carat's ring size guide shows how to find your size at home. If you are still deciding on both rings, compare shank widths on the engagement rings you like before you settle on the band.
High polish is the usual choice because it is mirror bright and matches the shine of most engagement settings. The catch is that every fine scratch shows on a polished surface. A brushed or satin finish has fine parallel lines and a softer sheen, and a jeweler can refinish it when it starts to look worn. Hammered metal is dimpled all over, which hides everyday marks better than either.
Here the metal is the entire design, so choose the one you enjoy looking at. 14K gold is the harder alloy and shrugs off scratches better than 18K, which has a deeper color but is softer. White gold owes its bright white to a rhodium layer that wears over time and can be redone. Platinum is white all the way through, feels heavier, and suits most sensitive skin; scratches move its surface rather than removing metal, leaving a soft patina.
Because there is metal all the way around, a plain band is also straightforward for a jeweler to size if your finger changes. Rare Carat resizes rings free in the first year and backs the setting with a lifetime manufacturing warranty; the resizing policy spells out how it works.