: Small wood pieces used to retighten the canvas if it becomes slack over time.

How to Use the Canvas Wedges That ... - Jackson's Art Supplies

: Measured in ounces per square yard (oz), weight determines durability and how much paint the surface can support. Lightweight (5–7 oz) : Best for quick studies or practice.

: The professional standard for archival quality. It is stronger, less prone to sagging, and has a unique "tooth" (texture), though it is significantly more expensive and harder to stretch.

You can find a wide range of canvas rolls at these reputable art supply stores: