An inflatable plug for sealing a pipeline includes a tubular member, a first indicator, and a second indicator. The tubular member has an inner surface and an outer surface that extends in an axial direction from a first end to a second end. The tubular member defines a central chamber configured to inflate to a predetermined pressure so that the outer surface of the tubular member expands to contact an inner surface of the pipeline. The contact between the outer surface of the tubular member and the inner surface of the pipeline define a contact length that extends in the axial direction. The first indicator and the second indicator are positioned on the outer surface of the tubular member. The first indicator is spaced from the second indicator in the axial direction by a predetermined length. The predetermined length is substantially equal to the contact length.