The reflectors are fitted by either using a special high temperature strong double sided tape or screwing them into the light fitting (we supply both tape with the fitting). It takes approximately 5 minutes per fitting to install. Installation involves removing the diffuser (if any), taking out the two tubes, attaching the reflector, putting one tube put back in and then replacing the diffuser after wiping it clean. In some cases it may take a bit longer than 5 minutes - some fittings have diffusers that are hard to remove. For some fittings you may need to cut out a hole for the starter. And in some rooms you might require an elevated platform to meet Occupantional Health and Safety standards for working at heights. But its been our experience in most cases that 5 minutes per fitting is all it usually takes. We recommend installation by a registered electrical contractor.