Just normal tempered steel cogs would be fine To My Pragmatic mind .. rather than Titanium ..
but Bike bling /weight weenieists are more willing to put the $350 out for Ti.
Back in the late 50's early 60's I added a steel 3 cog cluster to my AW3, English, Cyclo It think..
it was 1 piece of steel machined with all 3 cogs in 1 chunk, slid right on in place of the 1 1/8" cog & 2 spacers ..
No instructions to not use a wide chain in a derailleur set up back then, so I did .
fitted a steel triple crank too .. 3x3x3 a 27 speed . 3 shift levers .
