3/8" ~ 10mm is conversion. I am game on building a sump with 10mm outer walls and 5mm wier walls. Just finished drawing up a simple sump plan. $170 for a 8x4 is pricey, but it will never break if you bump the sump by accident.
Heck you can't beat the price in reality, if you are planning on doing a sump too. If you bought one of those custom sumps from the Doc's shop, you are gonna pay around $300.00 for the pro model. For that price, you can build your tank and sump and save money.
Maximo