S size 28cm(bottom length)*40cm(height)*17.5cm(bottom thickness),advising for grade 1-4

style A
L size 30cm(bottom length)*42cm(height)*19cm(bottom thickness),advising for grade 3-6


style B
L size 31cm(bottom length)*43.5cm(height)*20cm(bottom thickness),advising for grade 3-6

Maybe with 1-3cm size error.