I brought the y carriage plate 200x300 to build a custom prusa i3.
The plate was a very good rigidy for is weight, it suport by default a mk2/mk3 bed with 200x200 or 200x300. It allow to use 4 or 3 level screws. you can use it with 8mm bearings with or without casing or 10mm with case. In my case i using with 10mm bearing with aluminium case. for a bed with this size 10mm is the way to go.
I from portugal, i receive the order in less of 2 weeks and everting was well packaged.
Overall is a great product, 5 stars...