These columns are low pressure (max. 7 psig) medium wall columns with reservoir. With precision all-PTFE valve and drip-tip. Greaseless PTFE insert with GL-45 screw-thread attaches flow control valve to column. Two types ( Standard Column, Column with Fritted Disc) are available. Each type comes with six different capacities: 100 mL, 200 mL, 400 mL, 600 mL, 1,000 mL, and 2,000 mL.