* All lighters are pre-filled. MK Lighter Green Series "Connection" 50pc set Jet Flame (wind-resistant) Refillable with (11X Premium Butane) Slip guard rubber finish for in hand comfort Please use with caution. Note: Butane lighters may struggle to function properly at higher altitudes due to decreased air pressure and lower temperatures. Generally, when the altitude reaches about 1,500 meters (approximately 4,900 feet) or higher, butane lighters may start to experience ignition difficulties. This is because as altitude increases, the air pressure drops, leading to a decrease in the vapor pressure of butane, making it harder for butane to vaporize from liquid to gas, thus affecting the lighter's ability to ignite. The impact becomes more pronounced with further increases in altitude.