These shelves can be used for cone 10 firings, but we recommend that you use a 1" thick shelf if firing above cone 7. Shelves that are 5/8" thick can go to cone 10, but the weight of your clay pieces or the manner you support them may cause them to warp. All clays shelves are subject to warpage at high temperature and should be repeatedly flipped to remain straight. Because we have no control on how you may use your shelves we cannot offer you any warranty in this regard. Most any size rectangular is available but because there is little request we do not stock them,. We would be glad to order them for you. Price and availability on request. We no longer ship loose kiln shelves & post by UPS, USPS, FedEx. It has been to difficult to get them to ship unharmed. cordierite Kiln Shelf for 13" Diameter Kilns (Skutt 609, Cress 911) 9.5" Full x 7/16", 3lb RF147$6.75 Half Kiln Shelf For 13" diamter kilns (Skutt 609, Cress 911) 10" Half x 1/2", 1.5lb RF148$3.65 Full Kiln Shelf for 14" Diameter Kilns (Skutt 714) 13" Full x 1/2" 5.25lb RF136$12.80 Half Kiln Shelf for 14" Diameter Kilns (Skutt 714) 13" hALF X 5/8" 5lb RF144$7.13 Full Shelf for 18" Diameter Kilns (Skutt 818, Cress E18) 15.5" Full x 5.8" 9.6lb 85320-1$19.50 Half Shelf for 18" Diameter Kilns (Skutt 818, Cress E18) 15.5" Half x 5/8" 9lb P5405-1$9.75 Full Shelf for 18" Diameter Kilns ( Skutt 818, Cress E18) 15 x 16 x 1 octagon, 17lb. This thickness needed if you fire to cone 10. RF157$22.25 Half Shelf for 18" Diameter Kilns (Skutt 818, Cress E18) 8 x 15 x 1 half oct. 8.5lb. This thickness needed if you fire to cone 10 RF155$15.90 Full Shelf for 24" Diameter Kilns (Skutt 1027, Cress E27) 21" Full x 5.8" 16.3lb We do not ship these shelves via UPS. RF109$34.30 Half Shelf for 24" Diameter Kiln (Skutt 1027, Cress E27) 21" Half x 5/8" 9lb We do not ship these shelves via UPS. 7320$17.95 Full Kiln Shelf for 24" Diameter Kilns (Skutt 1027, Cress E27) 21" x 22" x 1" decagon, 26.4lb. This thickness needed if you fire to cone 10. We do not ship these shelves via UPS. RF159$49.00 Half Shelf for 24" Diameter Kilns (Skutt 1027, Cress E27) 21" Half x 1" 14lb. This thickness needed if you fire to cone 10. We do not ship these shelves via UPS. RF139$23.58 Half Shelf for 28" Diameter Kilns (Skutt 1227, Cress E28) 26" Half x 5/8" 12lb We do not ship these shelves via UPS. 85320-2$23.75 Half Kiln Shelf for 28" Diameter Kiln (Skutt 1227, Cress E28) 26" Half x 1" 19lb. This thickness needed if you fire to cone 5 and up. We do not ship these shelves via UPS 85332-1$37.65 Rectangular Shelves 12" x 24" X 1" 22lb RF163$27.15