According to ASTMF963, visual mobiles should keep out reach of babies. It has been recommended that baby mobiles should be hung at least 12 inches away from the baby. You don't want them to grasp these visual mobiles when they try to reach them.
Remember to remove visual mobiles when the baby has turned around 6 months old. Around this age, they can reach out and grasp the mobiles.
The Montessori visual mobiles available at our website should also be used according to these safety rules. Additionally, don't use them when the baby is sleeping and in their bed. Use them only when the baby is awake and on their "working" mat/movement mat because viewing visual mobiles is their "working time". Movement mat is like their first working table.
Just for your reference, the materials we use to make Montessori visual mobiles or the materials we put together for you as DIY sets have been tested comply with following standards:
-USA Consumer Product Safety Improvement Act, Sec. 101(a): Total lead content for substrate in children’s products
-USA Consumer Product Safety Improvement Act, Sec. 101 (f) and 16 CFR 1303: Total lead content in paint and surface coating
-USA Consumer Product Safety Improvement Act, Sec. 108 & 16 CFR1307: Phthalates content
-ASTM F963-11: heavy metals contents