Its my opinion, that if one wants bigger arms, "overall" body weight needs to "appropriately" improve, such as the "major muscle groups" (for example the upper and lower back, chest, etc, etc).
Personally, I believe that if one builds the larger muscles of the body, the arms (which are the facilitators of moving "some" of these larger muscles), will have no choice to get stronger/larger to balance out the needs of the larger and stronger muscle being worked or used.
Without the arms, a lot of major muscles do not move, just think about it some.The bicep and triceps are assistants in the major muscle movements.
Bench Press (pecs, shoulders,etc) you are involving muscle of the arms. Variant of rows (back, etc), you are involving muscle of the arms. Military Press (shoulders), you are involving muscle of the arms. Chin-ups/Pull-ups, you grab the bar with the hands/arms, and during the execution a whole mass of major muscle parts come into play to execute the entire movement.
The arms open the door to the larger muscle groups. Improve strength/hypertrophy of the major muscle groups and the arms will naturally follow in strength and/or hypertrophy.
IMO: Give your body "a reason" to have stronger and bigger arms, by gaining appropriate weight and building/improving the major muscle groups.
And, since they play such a critical role in the execution of the major muscle movement (s), build overall mass, and the arms will follow to compensate for its weakness comparison to the major muscle group its helping/executing.
Focusing/homing in on just the arms for size, is a mistake, IMO.
Instead, (IMO), focus on entire body improvement, and of course (if you wish, and appropriate for individual), one can include specific exercises for the triceps and biceps (but, I wouldn't have this the focus,--but rather just have specific exercises as part of a balanced program). If specific weaknesses, show up or develop, you can work on these.
I have good triceps development, but its not due to, for example, only performing decline triceps extensions and other triceps specific exercises, but rather the package parts of the other components of my routine that involve the major muscle groups. The same for the biceps.
If you want assistance with your program, open up a bit on your personal stats, and what you are currently doing, and we will be able to home in on more spefically-natured help.
Keep training, and be consistent, and good things eventually happen, trust me.
Best wishes
Chillen