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Only #25 chain is #25 chain, however, there is #25 (standard -duty) and #25H (heavy-duty) #25 chain. Virtually all electric scooters, bikes, and go-karts that have a 0.25" pitch chain use #25H chain. 

T8F chain is what we call 8mm chain and it is the type of chain that is used on electric scooters, bikes, and go-karts that have an 8mm pitch chain.

BF05T chain is gas engine timing chain. BF05T chain is often mistakenly sold as 8mm pitch chain for electric scooters, bikes, and go-karts. BF05T chain has an 8mm pitch, however, its roller diameter, width between inner plates, and pin length is different than T8F chain. Its smaller roller diameter is likely to wear out T8F sprockets faster than T8F chain will, and its smaller pin diameter will cause BF05T chain to wear out faster than T8F chain.

Here is a dimension specifications chart for both T8F and BF05T chain which shows the size differences between these two chains.

44 tooth wheel sprockets for #25 chain that fit the Razor E300 scooter are not available. However, we have a solution to be able to install a 44 tooth sprocket for 8mm T8F chain onto the Razor E300. 

Please read our reply on this forum topic for more information: https://electricscooterparts.freshdesk.com/support/discussions/topics/1000088388

#25 chain is an imperial size and not a metric size, so 6mm chain is not the same as #25 chain. 

#25 chain will not work with 8mm sprockets and 8mm chain will not work with #25 sprockets.

Here are the dimensions that need to be specified when ordered a custom-made chain sprocket which will be bolted onto a 4-hole freewheel.

Here are the measurements for #25 and #25H chain.