As I said before, Philips & certain other models have built-in adjustable combs. The settings can be changed in 0.5mm increments by a click type slider. The cheaper ones change in 1mm increments.

https://www.amazon.com/Philips-BT7201-Rechargeable-Trimmer-Vacuum/dp/B01E6E3JJ4/ref=mp_s_a_1_110?dchild=1&keywords=philips+trimmer&qid=1588932867&sr=8-110

https://www.amazon.com/Philips-trimmer-adjustable-length-QT4005/dp/B00IMTAI1M/ref=mp_s_a_1_112?dchild=1&keywords=philips+trimmer&qid=1588932867&sr=8-112

https://www.amazon.com/Panasonic-Mustache-ER-GB40-S-Cordless-Adjustable/dp/B008KEJ1LM/ref=mp_s_a_1_115?dchild=1&keywords=philips+trimmer&qid=1588932915&sr=8-115