The Cupped lids of the provap are inexpensive. It made of heat resistant plastic and holds the Oxalic acid. I have several, I place one on each hive top preloaded with 2 grams of Oxalic acid. Then I approach the hive, turn the provap upside down, press the lid on, insert the gas tube into the hive, turn provap rite side up and 8 seconds later, finished and in to next hive.
I stuff soft flexible foam into the entrance so the OAVgas does not escape. After about 2 minutes, I remove the foam to open the entrance and in another 2 minutes all appears normal. I have precut foam. I will post a pic.
Van