Adjustable Resistance: The resistance strength of this power twister can be adjusted by rotating the knob,the range is:You don't need to buy new ones when your strength level increases,it applies to any stage of arm strength training enthusiasts.Easily turn the knob left or right,increase or decrease the resistance to meet your needs in different training stages,accompany your entire fitness career.But please choose the intensity that suits you so as to avoid muscle strai. Easy to use and Storage: The bottom made of ergonomic PU handle, which is wear-resistant and non-ip, and has a comfortable grip. There is a buckle on the bottom of the handle, very convenient to storage, when opening the package, please hold the handle with both hands, use your index finger to open the buckle, and you can use it. Strong and Sturdy Material : The hydraulic power twister is made of high-density dual-carbon steel, reinforced with a ribbed design, and reinforced with 10 screws. Very metallic, not easy to deform and break. The core is a fully sealed hydraulic cylinder, which has a simple structure, reliable operation, adjustable resistance, and is very safe. It can provide stable resistance strength and will not weaken with the passage of time. Totally enclosed Hydraulic Cylinder: Unlike other spring based exercisers,our power twister adopts totally-enclosed hydraulic cylinder which offers you stable resistance strength,will not weaken over time With unique safe hydraulic adjustment system principle,even if you change the resistance,the opening angle of the arms doesn't change,the motion track ao doesn't change,so you don't need to change arm movements,and what's more,you can fully open your arm even you reduce the resistance Golden Ratio Triangle Structure: The unique golden ratio triangle structure with 10 reinforcement rivets maks the arm trainer more load-bearing capacity,always keep it in a stable state,ensure the safety for using.So whether you are a novice or a veteran,it will be very suitable for you.Perfect for exercising your wrists,arms,shoulders,chest and back at the same time,developing your grip,building strength on your fingers,wrists,and increasing the muscle strength of the upper body.