Clamping pressure is also a key design parameter to consider when selecting a TIM. For low clamping pressures, a gap filler is recommended as they are generally soft enough to conform to the surface of a device and provide a low thermal resistance path for heat flow. For higher pressures, a grease or PCM is recommended. When using a silicon based gap filler, too much pressure (say, above 45% compression) can result in silicone oil bleed. This will, under certain conditions, be detrimental to the life time and performance of a device. However, when using a PCM or grease, too low a pressure will prevent a good heat transfer path from being achieved; this could also significantly shorten the working life time of a device.