Regular sand-filled systems don't work and are too hard!  RT990-Plus requires no sand infill and it can be seamed in any direction unlike RT990.  You can hit down and through the ball; the club face won't bounce off the surface!  Also, a real tee can be inserted anywhere on the surface which helps to evenly distribute wear.  RT990-Plus is available as both a tee-line surface and as a hitting mat.