OneUp 42t+16t was £57 ($90) posted using paypal.
RAD cage was an extra £22 ($35) when posted at the same time.
Shipped from the UK and arrived in 2 days.
I first bought the 42t+16t kit without the RAD cage and fitted them one by one going for a quick ride in between as I wanted to find out exactly what difference each part did. Fitted with new 30t Blackspire Mono Veloce chainring, SLX M675 medium cage mech, XT cassette, SRAM chain and Zee shifter (I like the clunky/positive Zee shifting) .
Compared to 2×10 I lost the top and bottom ratios. I can’t remember ever using the 36/11t in the Alps this year except on short downhill road linking sections so won’t miss it. Had to put the B screw on the limit to get it to shift up to the 42t which resulted in less than snappy shifts lower down the cassette. Noticed the big jump without the 16t pretty much straight away and for me it would get annoying after a while as with the 30t it’s right where I’d be on the flatter/slightly undulating pedally sections of trails.
If I’d just gone with the 42t I’d be pretty disappointing with the low down shifting.
The 16t solved pretty much solved the jump in gears although the 3t jumps rather than 2t are still noticeable but as mentioned by other forum users above doesnt quite shift as well as the shimano cogs it replaces. I took a 16t from and old ultegra cassette I had lying around and once that was fitted I couldnt tell the difference in shifts compared to the cogs either side performance wise although it was still a little sluggish due to the B screw.
The shifting performance was something I know would annoy me over time so I ordered the RAD cage to see what difference that made for myself.
Then fitted the RAD cage and re-adjusted the b-screw. The sluggishness was pretty much gone. Not completely but I’d say 80-90% back to how everything shifted with the original parts. The RAD cage is the missing link which makes everything work together pretty much as OEM.
I didnt try the Rad cage with the OneUp 16t cog. I think that would work a lot better that it did with the standard SLX cage as the OneUp 16t cogs shifting could only exacerbated the extra distance of the mechs top pulley from the cassette. With the mech closer to the cassette I reckon the shifting would be much better.
If I was doing it all again and didnt have the Ultegra cog what would I buy?
With hindsight I’d buy the 42t+16t kit along with the RAD cage at the same time. If my current mech wasnt a mid cage one I’d take it off (I used all the old drivetrain to upgrade my XC bike to 10sp) and keep it as a spare if I only had the one bike. Only then if I wasnt satisfied with the OneUp 16t shifting would I order a new Ultegra cog which is easily fitted afterwards rather than the more involved mech stripdown to fit the RAD cage.
Hope this helps!