CRL Wood's Powr-Grip® ABS Handle Vacuum Cup is a value priced vacuum cup for use with flat glass. The ABS polymer used in the pump and handle makes the Cup lightweight, strong, and rust-resistant. A red-line on the pump's plunger indicates the vacuum level of the W4000. When the diameter Cup is attached completely, the plunger is partially hidden inside the pump and the red-line is not visible. A visible red-line indicates vacuum is not sufficient for lifting. If the red-line starts to show during a lift, a check valve allows the user to re-pump the Vacuum Cup without losing the remaining vacuum. When the lift is completed, a release mechanism allows air to refill the evacuated space under the Vacuum Pad, so that release is complete.