Very happy with the product and Kensui team (answering and solving any questions/problems)... I just bought a second pair (plus other products)!

Purchased 2 weeks ago with the dumbbell extensions. Performed dumbbell chest press, shoulder press, lateral and front raise, dumbbell curls, shrugs and dumbbell squats. I have loaded each dumbbell from 15 to 90 pounds and they felt very secure. The end caps do not come loose, I would have to tighten my previous adjustable dumbbells with the spin collars between sets and the bar would stick out the side making most exercises difficult. You can set the adjustabells on your thighs like regular dumbbells without pain and bruises. This is a solid purchase and I recommend buying for a home gym, will save alot of money in the long run.

These dumbbells do everything they purport!
A couple things worth pointing out though:
1. you have to be super careful not to drop or knock these as they are still being made from plastic.
2. Do not overtighten them, first of all it's unnecessary, and secondly everything is circular so there is no way besides brute grip strength and a good twist for getting the handle loose.

These work fantastically well! Could not be happier with this purchase!

Thanks for reaching out. I really like the adjusta-bell and it really expands some of my key movements without buying expensive dumbbells.
The only tough part is getting the weights off once I tighten them onto the device. I actually have not been able to get my ten pound plates off and have just left them on as unscrewing the attachment is too hard. I'll have to find a tool or something to figure it out. I can only get one side loose buy using the opposing leverage of twisting the weight plates.