Galaxy S5 fits in, however rubber belt very short, nothing for strong upper arms

The phone fits in your pocket, but you can not get more then the buttons for volume control and / or on-off switch for your mobile phone. Furthermore, the rubber belt is relatively short. Usable length is 20-25 cm, which is already very tight.
Men with muscles should get into trouble here and also people with strong arms due to obesity have here certainly no pleasure in it.

recommended due to the low price, however, limited since not usable for everyone.
The "Rubber Band" to fix the arm has a length of 25cm. Measure this better times previously on your arm out and considering that it is Velcro, which takes away so again a few cm.