Make sure that when you choose the size you allow some wiggle room to move the longarm over the edge to change the bobbin. The best size would be about 4-5" less than the throat of your longarm. EXAMPLE: 26" throat works best with a 19" Red-E-Edge. 16" throat works best with a 12" Red E Edge. Red-E-Edge Clamps are used to hold the sides of quilts loaded on ANY Longarm machine. Red-E-Edges are the BEST way to ensure you NEVER have to deal with tucks on the back of your quilt or wavy edges ever again. Using just one small clamp may leave you with uneven tension....causing a wavy border. No clamps mean you run a risk of a tuck on the back of your quilt. These lightweight side clamps hold securely and evenly across the entire side of your quilt. Red-E-Edges ensure evenly spaced tension, so you don't get uneven borders from a single point of a small clamp. All New UPDATED Red-E-Edges are designed to snap shut easily, open easily and still hold your back fabric with the perfect level of tension! You deserve the best. Red-E-Edges will make your quilting on ANY machine easier. Less time fussing means more time quilting.