95% of the time I use 3 walls (1.2mm), 3 bot layers, 4 top layers and 20-25% cubic infill. Not sure why you'd do 1mm but there might be some good explanation. Probably to gain time but still, I'd rather go for 3 walls and keep my 0.4mm per wall so the slicer uses the flow rate I calibrated instead of multiplying it to achieve 0.5mm walls. More @Wikipedia
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