The middle layer
A quilt sandwich has a top, batting and backing. Quilting stitches hold them together. Batting is also called wadding.
Loft is only one part of the choice
Low loft is relatively thin; high loft gives more fullness and relief around quilting. These names do not have one universal inch measurement. Fiber, density and quilting affect feel and warmth as well as loft. Check the actual product’s care instructions and maximum distance between quilting stitches.
Leave the required overhang
Batting normally extends beyond the quilt top while quilting. Ask your quilter how much they require. A 60 × 72 inch top with 4 inches extra on every side needs 68 × 80 inches of batting. Use the batting size calculator to choose the extra and compare example package dimensions.