The York Fitness 20kg Black Cast Iron Dumbell Set comprises the following:
When one spinlock bar is loaded with two 2.5kg plates, two 1.25kg plates, and two 0.5kg plates, the total mass is 10kg, making the total mass in this set 20kg. Using different (symmetric) combinations of weight plates, each bar can be configured to a total mass of 1.5kg, 2.5kg, 4kg, 5kg, 6.5kg, 7.5kg, or 10kg.
If you wanted to focus on unilateral work (lifting just one dumbell at a a time) you could take the plates off of one bar and use them for a heavier total weight on the other bar. Each spinlock bar can hold four 2.5kg plates, and four 1.25kg weights for a total mass of 16.5kg. Alternatively you can buy additional York Fitness Black Cast Iron plates of varying masses if you need to increase the weight of both bars at the same time.
I did originally buy a dumbell set thinking that I'd occasionally just lift a dumbell a few times while sat in front of the TV. But my lack of imagination was exposed when I found the unexpected extra which comes with this set: a poster titled "Dumbell Exercise Programme By York Fitness".
This A2 poster gives brief guidance on developing a weight training programme, including safetey warnings, and notes on stretching exercises, warming up and technique. Sixteen different dumbell exercises are illustrated with colour photographs and captioned with guidance on performing the exercise with the correct form, and a key explains which exercises relate to each muscle group (chest, shoulders, back, legs, arms and torso). It is an excellent introduction for someone who has had no previous knowledge of weight training, and while I did begin by simply working the biceps and triceps in my arms, I was soon also working the shoulders, chest, back, legs and abdomen.
Once you've slid the desired weight plates onto one side of the spinlock bar you need to screw a grey vinyl spinlock collar right up against the weight plates so that it holds them tightly in place. I couldn't find guidance on which way around the collars should be facing, but it seems that the strongest hold is achieved if you screw them onto the bar with the narrow, circular side closest to the plates, and the wider, cog-shaped side on the outside. Secured like this, the spinlock collars have held tight for me after months of use.
I rarely loosen the spinlock collars, because I don't change the weight plates often. Even though it's realtively straightforward to undo the collars, change the weight configuration, then attach the collars again, this takes time and energy which I don't have during a workout session. If you regularly loosen and re-attach the collars, it's possible that the collars may become looser over time, so keep an eye on this. However you train, make sure to check that the collars are tight and the weights are held firmly in place before each exercise, otherwise you risk injury if the plates come away from the bar.
The rubber grips on the spinlock bars give a very firm hold even with clammy palms, but you won't fail to notice the stench of rubber on your hands after a session. More of a problem is the calluses you'll get on your hands if you have soft skin. If your hands are your fortune, it may be wise to buy some gloves designed for weight training to reduce wear and tear on your palms.
The length of the spinlock bars enables them to be loaded with numerous weight plates, but it also means that the unused length can get in the way for some exercises. For instance, in the bench press you aim to bring the weights close together at the top of the motion, but the length of the bars limits how close your hands can get. However, almost all configurable dumbell bars that I've seen are at least as long as these spinlock bars, so this is a general observation rather than a problem unique to this set. And for most exercises it's never a problem.
To avoid having to change the weight plates frequently I actually own two York Fitness Black Cast Iron Dumbell Sets: a 20kg and a 15kg version, identical but for the set of weight plates provided. Both sets have served me well for several months, and I would recommend either of them to someone starting out in weight training. The bars and plates are solidly made, the collars hold tight, and the colour poster provides a good introduction to weight training with dumbells.