Questions about Epson T0711h

Warning: I have an Epson Stylus SX110. These (original) toner cartridges do not fit in my printer, although listed under "suitable for". When comparing with "Epson T0711 DuraBrite Ultra" (expensive 18.80 for 1 cartridge) I noticed that the shape was not the same. After I adjusted the shape with a pocket knife (cough, cough), it worked for a while. Then when the cartridge ran out, suddenly an error message ("not original cartridge" or something like that) came up and it was no longer accepted. After using a pocket knife, I was able to make the second one fit again and it is currently accepted.