I agree with both SMB1 and Septic1 In addition, the installation of guide rail for VNA is not only costly, but prohibits access to ground floor pallets with a hand pallet truck. The wire guiance option is again costly to install both in the warehouse and on the machine. Guidance systems, either rail or wire require ongoing maintenace costs. Choosing VNA also severely restricts machine availability in the event of breakdown or busy times. The transfer aisles for VNA machines need to be much bigger which will reduce the storage density (Defeaing the whole object) The need to lift a pallet over the guide rail at groud level reduces the overall available stacking height. The 150mm saved can mean the difference between stacking 5 pallets or 6 pallets high. 25% of storage density lost at a stroke.