DC 3 I thought that filling the base with water was sufficient, however soon it began to leak. It is probably better if you fill it with sand. Anyway this is not very portable and is not very sturdy. It really isn’t made to be adjusted frequently or moved from place to place. However my boys use it everyday so I decided not to return it. It’s a shame because I think cheaper versions are available. It was not that difficult to assemble but to be certain it was tight was a bit of a hassle.