IKEA Alex drawer unit ships with flimsy and tiny plastic feet, ether glued or inserted into single hole. Extremely easy to brake. You can replace with these sturdy ones. 8mm high. 

Designed for 32mm square hole pattern at the bottom of the unit, which mine already had. If yours does not have it - feel free to drill it yourself. 

Requires 4x 3.5x20mm (16x total) screws with conical head per feet (16-18mm long ones will work as well, but be very careful when screwing in). 25mm will be too long.