The Rim Mount is an adjustable mount that fits on top of a spotlight. This item requires drilling and a pop rivet gun with 1/8 drill bit and rivet nails to install.
Standard issue does not include the rail for the thermal. The rail is available - item code: SRTWR
Also available is an optional long rail to help shift the weight on a spotlight thus avoiding the remote wanting to lean towards a mounted thermal on top. Available here: https://www.eagleyehg.com.au/smartrest-gun-rests/smartrest-parts-accessories/smartrest-rail-for-spotlight-srlrb.html