My 1st set of ergon grips from about 3 years ago did not have that little internal lip. But the pair I bought about 4 months ago did have it. I solved it with a round, aka rat tail, file, aka rasp. I filed out the offending bit of plastic until they slipped onto my trekking bars in the same way you're intending. They now work fine. Get a round file/rasp & remove that lip & you're good to go!