High-quality product, 100% compatible with the more expensive Leading Brand (Lego) as advertised.
These large 50 x 50 stud baseplates are stiff enough to provide a good stable building foundation, but with enough flexibility to not crack if the surface you are using them on is slightly squishy and uneven (like a rug). Of course, for the longest life and best performance you should obviously use a flat hard surface like a table.
Despite their large size, they have the same fine tolerance as BricTek's smaller base plates. Two or more of these large baseplates can be laid side-by-side to create one continuous building surface, with no gaps or overlaps.