How much weight can each dumbbell hold?

The set totals 20 kg across two bars, split between four 1.25 kg plates and four 2.5 kg plates. Each dumbbell carries half the plates plus the bar and collars, so the maximum per hand is well under 10 kg of plates.

How fast is the weight change?

You loosen the spinlock collar, slide plates on or off the long sleeve, and tighten the collar again. It is quicker than swapping fixed dumbbells for a whole set, but slower than a dial or pin system.

Is it a good alternative to fixed dumbbells?

Yes for small spaces and light-to-moderate loads. It replaces a rack of fixed pairs with one compact set, but the top weight per dumbbell is lower than most fixed dumbbell ranges.

Two dumbbell bars, four 1.25 kg plates, four 2.5 kg plates and four spinlock collars. No stand or case is included.

Are the collars secure during exercise?

The spinlock collars thread onto each end of the sleeve and are designed to hold the plates in place. Check them are tight before each set, as with any spinlock set.