12mm table

Personally I would avoid buying a 12mm indoor table. The wood top is too thin so you won’t get a very good bounce. The entire table is likely to be more flimsy, as it’s a cheap product. As with most cheap products, it is more likely to break. 
 
The minimum table thickness you should consider is 15/16mm. The best tables are 22-25mm. These ae more expensive, but are will last 10-20 years (and more) if you look after them.
 
Here are some more tips about buying a table tennis table: Guide to buying a table tennis table