Replacement firebox refractory for Classic Edge 550 models. Although they are pictured as a pair, only one refractory is shipped per order. If you require two, please order Quantity: 2. This item is 1/2 of the upper refractory, two upper refractory (p/n 4050033) are required per furnace. Replacement rope (p/n 809) required: 4 ft.