The vest as a standalone garment rather than as a component of a three piece suit occupies an interesting casual territory that’s become genuinely wearable over the last few years as the layered relaxed approach to dressing has made it easier to justify things that might previously have seemed like they needed a specific context to make sense. A knit vest or a more structured waistcoat style worn over a long sleeve tee or a shirt creates a layered look that adds visual interest without the bulk of an additional jacket. The key is treating it as a deliberate layer rather than a remnant of something more formal that’s lost its accompanying pieces. Keep everything else in the outfit simple and the vest adds something without dominating. The fit needs to be right through the torso because a vest that’s too large just looks like you’ve misplaced your jacket.