Citizen COBs are one of the most economical choice for DIYers. The CLU-1825 series is the industry leader in efficiency and typically outperforms the popular CREE CXB3590 by up to 10% or more at most currents
The CLU-1825 series is a nominal 50V COB which can operate up to a whopping 5.75A max (approximately 364W!). Best efficiency is seen below 160W with this chip .
Can be mounted directly via handy mounting holes, for solderless option this chip uses BJB Holder model 47.319.4160.50
Precut Arctic thermal pads are available here
90CRI offers an enhanced red spectrum with the red peak centered around 630 nm
Tech specs on the COBs are found on the Citizen datasheet here
Thermal Pads are 0.5mm thick Arctic brand, cut to size from larger sheets. You can read about them here