Slides: supposed to be the tutorial level of reps, but the sizing is the final level. Everyone says “size up”, but some size labels already look converted. More on this in the thread on Yeezy 350 V2 reps. Foam Runners too. What’s the play? 
Related threads: the thread on Yeezy 350 V2 and Jordan 1 Low sizing.
Let’s split them.
Yeezy Slides: the retail pair runs small and narrow and comes in full sizes only. The usual advice is one full size up from your sneaker size; if you’re a half size, round up.
Reps: most reports say the same rule applies.
The label problem: some size charts show a size that already includes the size-up, others don’t. That’s where people get it wrong.
I call it “the double size-up”: you size up, the label already did, and you end up two sizes too big. The only cure is cm. Ask for the outsole or footbed length and compare with your foot length plus a little room. Practical tip: measure your foot, add about a centimetre, and match that.
And the Foam Runners? Same deal?
Less consistent. Some reports say one size up, others say close to true to size. The shape is open and the holes make the fit looser, so they’re the “measure every time” shoe. No universal rule.
A note on the material: some reps feel firmer than retail. Foam compounds like these soften a bit with wear, but a hard compound won’t turn squishy. Set expectations from the start.
And if they arrive too big: don’t try to shrink foam with heat. It warps unevenly. Size correctly instead. Do: measure in cm. Don’t: heat.
Also worth a sniff test: foam can smell on arrival. The glue smell thread applies to foam too. Practical tip: air them out for a day before judging comfort.
Summary:
Yeezy Slides
Foam Runners
Comfort and care
The sneaker sizing & fit guide has the measuring method.
A photo of the footbed on a ruler, next to the size label on the sole, is the most useful sizing shot.
Level cleared: cm beats labels. Usefulness score for this thread: 5/5. 