In this university study, sections of an integral calculus course were randomly assigned to either a control or treatment group for a lesson on volumes of revolution. Both groups were given similar collaborative tasks, but only the students in the treatment group were given access to a set of 3D manipulatives. Pre- and post-assessments were administered to measure student achievement and confidence on the tasks comparing results for the control and treatment groups as well as for the male and female students. No statistically significant differences in student achievement were detected for the control or treatment group or by reported gender on either an immediate posttest or a delayed posttest. There was statistical significance in confidence after engaging in the 3D manipulative tasks favoring the treatment group. However, further inspection by gender revealed that while males in the treatment group were more likely to report higher confidence ratings than males in the control group, the reverse was true for females.