Modular heat sinks

The invention relates to modular heat-dissipating housing covers for opto-electronic modules, e.g. transceivers. The housing covers according to the present invention are constructed out of various different parts, which provide different levels of heat dissipation depending on the desired implementation, while maintaining a seal against EMI leakage. Extra heat sinking portions are provided to dissipate heat generated from specific heat generating sources. The extra heat sinking portions are configured into a shape and/or out of a material that provides more thermal dissipation than the standard cover provided. Independent control over the different heat sinking portions enables a better fit and appropriate dissipation.