After being caught without a cap too many times, I now stock them in my house. You can get ‘em for pennies compared to how much they cost from an HVAC company and it’s just a few screws to replace them. Guarantee I’ll need a new one every summer - YMMV. nostr:note1e7qnnrhpqmta787e3n6599ftgaznplweuk4qefpm5wns5at8my9q7g4zxd