Short answer: no, not with the parts either company sells. An UPPAbaby bassinet will not mount to a CYBEX Gazelle S frame, and the reason is more specific than "different brands".
Why it does not fit
This is a polarity problem, not a size problem — which is why it surprises people who assume a bit of trimming would do it.
On an UPPAbaby Vista, the bassinet carries a female socket that drops down onto a male post built into the frame. On a CYBEX Gazelle S, the frame carries the female receiver, and it expects the accessory to present a male fitting.
So you have two female halves facing each other. There is nothing to join. No shim, no spacer and no amount of filing changes that, because the missing part is not clearance — it is the post itself. An adapter for this pairing has to be male at both ends, which is what makes it a real part rather than a sleeve.
What we are doing about it
We are designing that adapter now. Both halves are on the bench — we buy the stroller before we design for it, and we measure the real parts rather than working from a published drawing.
It is not shipping yet, and we would rather say that plainly than take an order we cannot fill. If you want it, say so: tell the Fit Finder which pairing you need and we will email you the day it ships. Requests are how we decide what to build next.
The reverse direction — a CYBEX carry cot on a Vista
Same wall, mirrored. If you are moving the other way, see will a CYBEX carry cot fit an UPPAbaby Vista? — both halves of that pair are being designed together.
What does fit a Gazelle S today
Three Stroller House parts ship for the Gazelle S and eGazelle S right now:
• Lower-Slot Basket Adapter — carries the CYBEX shopping basket in the lower slot so the seat, carrycot or car seat can ride above it at the same time.
• YETI Hopper Flip Cooler Mount — carries a Hopper Flip 8 or Flip 12 down in the lower slot, inside the wheelbase where hanging weight belongs.
• Balance Bike & Scooter Holder — a pair of cradles on the upper side frame tube, so a balance bike or a kick scooter rides home instead of being carried. Either side on the Gazelle S; the left tube only on the eGazelle S.
The fit guide covers what fits what across the whole catalog, everything we make for CYBEX is in one place, and all adapters lists the lot.
Before you buy any adapter
Every Stroller House part must come off before the stroller is folded. That will be true of this one too when it ships. See installation and safety.
Stroller House is an independent aftermarket brand. We are not affiliated with, sponsored by, authorized by or endorsed by UPPAbaby or CYBEX. Brand and model names identify fitment only — see our trademark and compatibility notice.