I've been searching for sturdy, clamshell-style RFID cards for my access control project, and these T5577 cards hit the mark perfectly. The thickness (1.8mm) makes them feel premium in hand - way more durable than those flimsy hotel keycards we all know.

Programming them with my Flipper Zero was a breeze. The blank slate is actually an advantage - no pre-programmed IDs to conflict with my system. I successfully cloned my EM4100 tags within minutes, and the rewrite capability means I can repurpose them as needed.

The CR80 size fits all standard readers, and I've tested them with multiple 125kHz systems without issues. At about $1 per card, they're an absolute steal compared to proprietary solutions.

One thing to note: they arrive completely blank (as advertised), so beginners should be ready with proper programming equipment. But for tinkerers and professionals, these are fantastic blank canvases for any RFID project.