Smartlet One is compatible with the Doxa SUB 300. All steel references use 20mm lugs, natively supported with no adapter. Installation uses the standard spring-bar system — no modification to the watch, fully reversible in seconds.

The SUB 300 appeared in 1967 with an orange dial that professional divers could read at depth. Doxa did not design a fashion watch — they designed an instrument. Saturation valve on the caseback, decompression table on the bezel, uni-directional ratchet. The orange became iconic because it was functional. The Doxa collector community is among the most knowledgeable and opinionated in the watch world. Sharkhunter, Divingstar, Searambler — they know every colourway and its history. Smartlet understands that audience.