Maximum permitted weight is 20 kg, dimensions are the following (height, width, depth):
XS - 8,5 x 19 x 60 cm
S - 8,5 x 40 x 60 cm
M - 18 x 40 x 60 cm
L - 37 x 40 x 60 cm
From: https://www.dpd.com/ee_en/home/pickup_network/frequently_asked_questions