I want to change my SX pg1210 12 speeds sram cassette and i don't know if it's ok to buy the same cassette or NX PG1230. I know just i need a heavy duty cassette for my ebike, it doesn't matter the weight. My SX was good for almost 8000km touring mtb but with the new chain X01, the 4 smalest gears skips sometimes when i pedal hard. So what's your advice and what's the difference between pg1210 and pg1230 ? Please help me with your advice. Thank you for your help !