I have the Spark Plugs you mention - the foam is very pliable and you roll it between thumb & forefinger before popping them into your ear - the foam then expands to fit snugily in your ear - they are comfortable & havent popped out on me tho' I'm only walking with mine in
Soundwise I was quite impressed for the money but they are VERY bassy so u need some sort of bass management on your source or I'd give them a miss ...
HTH - Paul

PS - They come with 2 sets of pads - not sure how long they'd last - I've had mine for about 3 months but dont use them every day ...
__________________