First off: this is fundamentally a good marble run! Lots of bits, you can build it tall, stable, whizz clunk rattle. But...
Bought this with the "tin of 100 marbles"
(100) Marbles in a Tin- a recommended pairing - and those marbles are too big to fit through some of the holes! You get a small bag (~15) marbles with the run, and these work fine. Close comparison between these and the others (and other marbles in the house (generally found under sofas, beds etc)) shows that they are smaller than what would appear to be 'standard' marbles. Are Continental marbles a different spec to UK ones?
Also, when it arrived the inner product box appeared to have been opened, and a couple of important whirly wheel bits were missing. The boy (3yo) spotted this on comparison with the box - oops, shouldn't have taught him to count, I guess.
So, it's gotta go back, much wailing, gnashing of teeth to follow, guess we'll go get the Galt one instead - I know that one fits 'normal' marbles!