Sukasana (cross-legged) to Virasana (kneeling) can be done on the SIT3.
A lot of meditation benches or cushions or chairs will usually only support the sitter in the kneeling position, or in the cross legged position. With SIT3 and with the SitBlox the sitter can be supported in either position.
SitBlox also offers a lot of variety when it comes to sitting on the floor during meditation. For example, when sitting cross-legged for a while it can be nice to change it up and kneel for a while.