They’re fine. A bit mushy compared to the stock membranes.
These are nice replacement pads. Mine are a little stiffer than the originals, but I actually prefer them that way.
I only bought these to have a ton of select button membranes so can't comment on the others, but the start/select stuff is good.
L+R buttons don't properly fit the GBA, it's like they're a tad bit too large and when you screw the back of the original case back in, The shoulder buttons get real tight. I got the Black Buttons with pink silicone pads. But the rest of the buttons work and feel very well. So 4 stars