Custom Longchamp Le Pliage, size 3 or 4 for birkin 30?

LVLover

Hermes Only
O.G.
Jan 18, 2006
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I need a Le Pliage birkin protector for my travels. I have read all over the forum that I need a large or an x-large. However, this is not how the US longchamp custom site sizes their bags. Do I need the size 3 or 4? I know the 4 will fit as it's a huge bag, but I would prefer to order the 3 if this works. Thanks so much!!

size 3: 13 x 12.5 x 7.5
size 4: 17.25 x 13.75 x.9