Astonishingly good!!
All my previous cats made use of a bog-standard Staywell cat-flap. I tried upgrading to magnetic locking devices, but to no avail. They've all been very intimidated by the VERY loud clunking as they went in and out.
My last two, Russian Blues called Hammer and Sickle, hated it. Hammer simply couldn't understand the 4-way locks at all, so promptly wrecked the flap!
The Russians died about 2 yrs ago, both aged 19.
So, after a break of two years I've acquired two British Blues, brothers named Jago and Bacon!! Don't blame me, my grandsons named them. They're now 27 weeks old, neutered, chipped, and vaccinated. They've been very curious about the cat-flap, and so, last week, my son and I trained them how to use it by 'posting' the cats in and out of the house for about 20 mins.
Whilst not silent, the light noise made by the locking mechanism doesn't worry them at all. The SureFlap responds quickly to their presence, and enables very quick entry and exit.
The cat-flap seems very well made with no sharp edges to catch the cats. Even better, it's run on batteries. It would've been a pain for me to run a mains lead and transformer to the door, so I was delighted to find a battery-driven flap.
Very easy to install, and large enough to accommodate a sure-to-be chunky cat!