Sp41 outer gear housing

I’ve given up trying to source some new gear cable sets (everything seems to be out of stock) but I’ve managed to find some stainless steel gear cables on their own and will need to buy the outers separate.

So my question is can I buy Shimano SP41 outers? Do these fit any road gear cable? Wasn’t sure if these were just for mountain bike etc or whether all gear cables from Shimano were the same

Yes, SP41 works with any derailleur cable, no matter whether it’s 1.2 or 1.1 mm wire.
Shimano recommended a different, much more flexible outer casing for the last bit of housing from the cable stop on the chain stay to the rear derailleur when they introduced their Shadow technology to road derailleurs (Ultegra R8000, Dura Ace R9100) but on most frames SP41 works perfectly fine even for that piece of housing.

No probs thanks.

I was wondering what the rs900 cable outer was for. I’m planning on fitting r8000 ultegra but will give it ago with normal outer as the rs900 like everything else is out of stock :weary:

On those rear derailleurs like your RD-R8000 the placement of the cable stop has changed. That piece of outer casing running from the frame to the RD now forms much less of an arc. When taking off the rear wheel on most frames with shortish chainstays the RD has to turn clockwise around its upper pivot - which no longer features a spring on a RD with Shadow technology.
With a stiff outer casing which runs nearly straight from the frame to the RD that rotation of the RD doesn’t happen automatically but against some resistance. Some users might even damage the outer casing while trying to make the RD turn. I guess that’s why Shimano opted to make that piece of outer casing much more flexible.
And because it runs nearly straight while in use it doesn’t have to support a lot of load anyway. It sits between a cable stop on the frame which is obviously fixed and a cable stop on the RD which is pulled forward against the “B-tension bolt” by the cage spring acting against the chain tension. So both cable stops don’t move as opposed to a traditional RD. If the cable path between those two stops was perfectly straight there would be no need for any outer casing anyway. But even with the slight curve it forms on most frames it doesn’t see much compressing forces which might make it necessary to use compressionless housing for the most precise translation of the brifter’s indexed movement into defined steps of the RD.
That said I still notice some improvement to shifting precision when using SP41 housing even for that last bit of housing, so I always bin the “soft” piece of housing which comes with the RD and replace it with SP41 or rather my preferred alternative from Jagwire.