The 38mm is for the 39-40mm hole and is the closest size manufactured so will require a bit of glue/silicone for security.
Pannier Liner Inner Luggage bags for KAWASAKI 1400 GTR Pair Motorbike
Powerflux Oil Filter for Kawasaki 1400 Gtr Abs 2015 to 2018 Motorcycle
Kawasaki 2006-2020 ZZR 1400 & GTR 1400 Racing Radiator Guard Zx14 ZX1400
AGM Motorcycle Battery for Kawasaki ZX12 GTR 1400 VN Quad 360 Replaces YTX14-BS
Fits Kawasaki ZG 1400 GTR 2008 - 2015 Yuasa Bike Battery YTX14 Pre-charged
EVAP / Canister Removal Plug Kawasaki ZX10R ZX6R ZZR 1400 GTR Versys 1000 650
