Bleeding brakes with a motorcycle bleeder?

[19sixtynine]

A friend gave me her MightyVac bleeder to use on my car, 4 wheel corvette disc from KORE3, and I noticed it's a motorcycle bleeder. The Motorcycle version does not have a pressure gauge. How important is the pressure gauge when bleeding car brakes? Should I not use this bleeder? What bad can happen by using a bleeder without a pressure gauge?

This is the bleeder she is letting me borrow, for reference