In the beginning, when day collars were first introduced into the BDSM community, they were only supposed to be worn during 'vanilla' situations where a 'normal' leather or steel 'house' collar was not acceptable.  If you were going out to dinner or going shopping or a family event, wearing a day collar symbolized that you were still under ownership by your Dom but ONLY you and other people in the lifestyle would recognize this. To the normal 'vanilla' world, you were just wearing a piece of jewelry.  Once back home, the day collar came off and the house collar went back on.   In the last few years though (especially after '50 Shades')  BDSM and Vanilla started to merge more and more making the day collar used more like the house collar and as something to be worn continually or '24/7.'
With this said, most  of our collars (except thin sterling cuffs, leather and pearls) and locks can withstand 24/7 continual wear.  They are solid high grade pure metals (925 Sterling, 14K gold, 316L Stainless Steel) that will not rust or be damaged with normal bathing.  They can even withstand salt or chlorine swimming (rinsing it off with clear water afterwards will stop any premature tarnishing).
Please remember that this is still 'jewelry' and should be cared for as any other high quality, expensive jewelry.  Day collars should match the person's lifestyle in the fact that if they are a hiker or a mountain climber you probably don't want a thin fragile chain that can easily get snagged and broken etc...  Many people think 24/7 equals 'indestructible.'  Common sense should be used when selecting the right collar.
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If you are not sure or have any questions, please just contact us.  We are always happy to help!