This magnetic cup holder can be install on any iron metal surface. You can install on marine boat , refrigerator, storage shelf , BBQ rack, ships, oven, golf cart ,treadmill, gardening machine, lawn mower,workshop file cabinets, black board,desk ,chair, wall etc.Powerful Magnet : This cup holder designed with powderful magnet, it can bear up to 1kg The super strong magnetic force enables it to stably hold a big thermos cup filled with water.It can be used not only as a cup holder, but also as a movable storage box.You can put gadgets,tools such as sunglasses, keys, cards, etc. The holder installed elastic fixing claw, securely hold a varity of bottles without spill or slide.Large Inner Diameter: The holder inner diameter can extend up to 8 cm. Big enougn to hold all kinds of bottles and small objects . It can place sippy cups , baby bottles, water bottles, coffee mug, drink bottles, beverage cups , kitchen Seasoning bottles cans etc.TWO Installation Methods : It can be directly install on iron metal surface due to its strong magnetic force and be used without any installation tools. It can also intall on other surface without metal . There is a screw hole on the holder. So it can be intall on any surface as you need.