Under The Sea. Using the Ikelite Trim Weight System for Underwater Housings, you can add up to five pounds of weight to your Ikelite Underwater system once you’re down under. Using this attachment makes your use of the housing unit more comfortable and balanced, while also overcoming positive buoyancy. This accessory simply screws onto the underside of the tray, without any tools needed, just by twisting the large attachment knob. Slightly loosening this knob will allow you to shift weight and achieve a balanced shot.