The disclosed technology includes couplers, nose pieces, and strain relief hubs for ablation catheter assemblies and methods of using the same. The disclosed technology can include a medical probe having a coupler having a first portion, a second portion, and a vent port. The second portion can slide between a first position and a second position. When in the first position, the vent port can be at least partially obstructed by the first portion and, when in the second position, the vent port can be unobstructed by the first portion. The medical probe can include a nose piece having an outer diameter of less than 0.14 inches and an aperture extending therethrough. The aperture can be sized to receive a catheter. The medical probe can include a strain relief hub having a first portion and a second portion and configured to be coupled to a handle of the medical probe.