Overall the belt works well. The 500ml bottles are a good size and sit firmly in their holsters, the added elastic to secure them is hardly needed but a bonus. The belt fits comfortably and there is little movement. The downside for me was the Velcro fastening. The loop it goes through can twist and on a run this morning it all came undone and I had to tie the belt in a knot to continue. Maybe the weight of the water was too much for the fastening especially added to being bounced around as I ran.
Good size secure bottles, sits comfortably