They are the best none cork pop ups available imo.
Flavours that have done me well include Fishy Peach, Pineapple/Butyric, Condensed Milk, Scopex Strawberry, Devils Dung (like a butyric acid kinda flavour, really stinks). I also use the their none flavoured hook baits for zigs, and for suspending alternative hook biats when the going gets tough.
I'd use any of the flavours they do tbh. That Kevin that runs it really knows what he's doing.