It is unfortunate that these adapters are even required. Ideally, I would prefer a unit where all I needed to do was change the blade. The adapter means that are 3 pieces needed to maintain the razor in working order, 2 things that can pop off, or 1 too many pieces.
The yellow adapters are almost useless, don't waste your money. I shave in a hot shower and the yellow adapters will soften in the warm water and come off after just a couple of uses, then you will find yourself in the shower with slippery hands trying to reassemble a 3 piece unit. It is dangerous and I am surprised that this hasn't been addressed. I would guess many guys have sliced a finger in the shower trying to do this, I have gotten close on several occasions. Buy the black adapter only, they will at least last you a while before having to go through this tortuous task of reassembling everything is the shower constantly.