This pattern comes in a large range of sizes and you only need 2 extra balls for the largest size due to the amount of colours used.
Measurements
To Fit 81-86cm 91-97cm
102-107cm 112-117cm 132-137cm
32-34in 36-38in
40-42in 44-46in 48-50in
Actual size 94cm 104cm 117cm
125cm 136cm
37in 41in 46in 49 1/2in
53 1/3in
Length 22in 22 1/2 in 24in
24 1/2in 25in
56cm 57cm 61cm 62cm
63.5cm