I bought a compressor last year primarily for a leak-down test and decided to upgrade the hose and ordered some couplings last year. So, got some DIY in mind and picked up a tempting offer on a TacWise 18G Brad Nailer last week from Amazon for £29.99 (Amazon lightning deals) - cracking little machine, never used an air nailer before and if you see it for £30, buy it ! lol Anyway...tried to plug the new male couplings into the compressor and it wouldn't lock in or seal. Now they are physically a different length but other than that being blindingly obvious, what else is different from them? So the existing coupler looks shorter like this and I bought these longer looking ones So what's the difference...apart from the length?