"Max Flow with 1.2?m filter: 20 lm-1 Max Flow, free air: 30 lm-1 Dimensions: W 200 x H 130 x D 216 mm Supplied with free battery and battery charger As SP021 but with a countdown timer. This enables the user to set the sampling time of either 30, 60, 120, or 240 minutes. When the set sampling period has been completed the pump stops and switches off. Also has the facility for continuous use."