Once you have removed the pillion footrests, fill the void left behind and cover those otherwise exposed holes in the sub-frame with the R&G blanking kit. 

This Footrest Blanking Plates have been specially designed to cover/protect both sides of the Triumph Tiger 900 GT/ Rally '20- & Tiger 850 Sport '21- (Pair)

R&G Footrest Blanking Plates/ Kits are easy to install, simply screwing into place in-place of the rear pillion pegs, covering those otherwise exposed sub-frame holes, that if left uncovered could result in corrosion of the frame/subframe from dirt, water and debris buildup.