For "L Shape" corner sofa cover or sectional sofa cover, you have to  buy 2/3 pieces

Item Name: Elastic Sofa Cover

4 Size Available:

1 Seater Sofa Cover: For Length 90-140cm Sofa

2 Seater Sofa Cover: For Length 145-185cm Sofa

3 Seater Sofa Cover: For Length 190-230cm Sofa

4 Seater Sofa Cover: For Length 235-300cm Sofa

Package Info: 1 x Sofa Slipcover

P.S: For "L Shape" corner sofa cover or sectional sofa cover, you have to  buy 2/3 pieces, attached pls check the "HOW TO CHOOSE SOFA COVER" picture for your reference.