What is Reddit's opinion of 38mm Poly Seal Screw Caps (fits most 1/2 & 1 gallon jugs) [Bag of 12]?
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I used flip tops and these, these work perfectly fine for me. I don’t know what you’re doing.

Also Yes OP your caps are done for. You can get 2 maybe 3 usages before they go bad. But they’re pretty cheap on Amazon. Home Brew Ohio Stuff Midwest... https://www.amazon.ca/dp/B0064OFP88?ref=ppx_pop_mob_ap_share

Also adding hot water to the bottles will make it easier to peal off the label.

They've lasted me about 4 months on average. Hope yours make it longer. Mine started leaking/letting air out so had to toss them. I bought these replacement caps and they work really well, but they don't bubble up as much as the commercial caps. They still do show a bit though.

https://www.amazon.com/gp/product/B0064OFP88/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Home Brew Ohio Stuff Midwest Homebrewing and Winemaking Supplies 38mm Poly Seal Screw Caps (fits Most 1/2 & 1 Gallon jugs) [Bag of 12] Black 83-2HJ4-5C57 https://www.amazon.ca/dp/B0064OFP88/ref=cm_sw_r_cp_api_glt_i_F4VPQJEXF0HJWVZCX3YH?_encoding=UTF8&psc=1

I am as well, Old Gt Bottles with a cap like this(cheaper at your local homebrew store) Have been working. however I use(and recommend because one growler takes up less space then 3 or so gt bottles) a Big growler with this cap for 2F and then strain into gt bottles that go straight to the fridge.

I switched out the regular growler tops for these

38mm Poly Seal Screw Caps (fits most 1/2 & 1 gallon jugs) [Bag of 12] https://www.amazon.com/dp/B0064OFP88/ref=cm_sw_r_cp_apa_dnBDyb93PHGC3

Work awesome and fit any 64 oz growler I've tried them on.

Most of mine still seal well. A few of them have been stripped. I bought some replacement caps on Amazon for $7.50 a dozen.

Replacement Caps- fits GTS bottles

If your local homebrew store sells 38mm polyseal caps, they should work. Otherwise, you can buy them on Amazon.

These are the ones I originally found but i live in Canada and didnt want to deal with cross border shipping on a little mom an pop shop, so I found basically the same thing on amazon