A mounting collar on a light fixture provides a compressive force between the illumination module and a light fixture. For example, a mounting collar that is fixed to the light fixture may engage with an illumination module to deform elastic mounting members on the illumination module to generate the compressive force. The mounting collar may include tapered features on first and second members that are moveable with respect to each other and that when engaged generate the compressive force. The mounting collar may include elastic mounting members on first and second members that move with respect to each other, wherein the movement deforms the elastic mounting members to generate the compressive force. The mounting collar may include an elastic member, wherein movement movement of the mounting collar relative to a light fixture deforms the elastic member to generate the compressive force.