I'm referring to the challenge of trying to get his entire cock into your mouth/throat balls deep. I've always enjoyed sucking bigger, thick cocks...8"-10" I've sucked a lot of big cocks in my day and many of the guys (married to women) never had their cocks deep throated by their wives and were desperately wanting to experience the feeling of their whole cock inside a sloppy throat. The excitement you feel when his cock flops out as you clutch his balls while sliding your tongue up and down it's length as it begins to grow. It begins to thicken and grow in length as you pop the head in and out of your mouth while gently messaging the balls. There it is...fully hard...That's the challenging feeling I'm talking about...You ask yourself, can I swallow this huge cock? Telling him how big his cock is, he smiles and says "Can you handle it?" Challenge accepted. The challenge of working that cock deeper and deeper into your mouth and throat inspires me to succeed as I occasionally gag on his manhood getting it sloppier and sloppier with the thicker saliva from within your throat. Then you feel the head of his cock penetrate your throat and like me you force it down your throat as his balls are jammed against your chin and hearing his moans of pleasure...CHALLENGE COMPLETED!