CRL Wood's Powr-Grip® 8" 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 8" (203 mm) 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.