Choosing a vacuum machine can be a matter of budget. The external suction vacuum sealers have been designed as a low-cost alternative to chamber vacuum packing. The external vacuum machines are often stainless steel construction, comprise a vacuum pump which sucks air out of a pouch from outside the appliance and a heat seal beam. Most external suction vacuum sealers work by drawing air from embossed vacuum pouches by placing the open end of the pouch underneath a lid, and by withdrawing the air, they heat sealing the pouch. The pouch works in conjunction with the machine to typically create an 80% vacuum but some more powerful machines have similar air reduction capabilities as a chamber machine – but no liquids can be vacuumed.