For 2017-2019 Rebel 300/500, 92569 (48 mm) or 17252 (60 mm).
(I put 92569 on my 2017 Rebel 300)
For the 2020-2024 Rebel 300/500, 17283/39913 (48 mm) or 17284/39914 (60 mm).
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For reference (older info)
Rebel 300 and 500 -Daytona Velona 17283 for 2020 – 2023 Rebel 300 – 48 mm diameter https://japan.webike.net/products/24200777.html … note: I am 100% sure 17283 also fits 2020-2023 500 – 1). Pedro Fernández Neri and Don Crawford put one on their Rebel 500, 2). a Japanese reviewer put one on his 500, plus 3). I have seen other references that it fits the 500 (see Amazon Japan ad below). 4). If you do not want to connect the tach to the ECU/coil, you can order an optional induction cable set ($8.41 USD) for determining the engine speed.
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For the 2017 to 2019 Rebel 300/500, you need to raise the tank to get to the ECU connection for the tach install. The 2020-up years is easier – they connect to the green wire on a ignition coil. They take a different Daytona tacho kit and harness.

For the 2020-up models, the harness directly plugs into the ignition coil (green wire).
If you do not want to connect the tach to the ECU/coil, you can order an optional induction cable set ($8.41 USD) for determining the engine speed.
On back of tachometer, the pulse rate can be adjusted: 1P-1r/1P-2r/2P-1r/30P-1r …. “1P-2r” is the setting for Rebel 300 and 500. It works for both because the tach reads rpm from one cylinder …. 1P-1r will show one half rpm