“Personalization is very, very important in our industry,” said Barbara Weichselbaum, chairwoman of the board for the wearable tech accessories brand WITHit, “whether it’s watches or wearables.”

And that is the focus of Band Candy, an accessories collection for the Apple Watch that the company debuted in July.

The collection features smooth silicon straps, available in four colors, and charms to customize them. There are also textured silicon straps, in two colors, which can be paired with decorative strips called sliders, in silver, yellow gold and rose gold colors, some embellished with crystals; and metal link bracelets, featuring a two-tone design, available in three neon colors.

The five sets of charms, each of which features four charms, include emojilike motifs such as red lips, a flowering cactus and a triple-scoop ice cream cone. Made of an ionic-plated alloy, enamel, and — in some instances — crystals, the charms can be attached through the strap’s holes, several of which are positioned near the watch face. That way, “you can really see the design,” said Bill Devaney, WITHit’s co-founder and chief operating officer. (The strap’s reverse has a long groove to ensure the backs of the charms don’t chafe the wearer’s wrist.)

The Band Candy products are sold on the WITHit website, and they were recently added to Macy’s site. The straps, which come in two sizes to fit all Apple Watches, are $20 to $35. The charms are $15 per set.

While the brand would not disclose sales figures, Mr. Devaney said they had “taken us by surprise.”

Marta Indeka, the senior foresight analyst at the Future Laboratory, a consultancy in London, said that WITHit has created “the Crocs of watches” — referring to the popular footwear brand that allows wearers to customize shoes by snapping on charms, called Jibbitz, that depict letters, images and characters.

Similarly, she said, the Band Candy pieces allow owners of mass-produced Apple Watches to personalize their timepieces. “They all, in the end, want the same thing,” she said, “but they want them unique.”

The luxury world has had a similar focus in recent years, with companies including the Bamford Watch Department in England and Jurmo Watches in Finland customizing watches.

In recent years WITHit, which was founded in 2004 in Las Vegas by David Nelson, Phil Grandinetti and Mr. Devaney, had decided it needed to invest in itself or to find a partner that could do so. And in early 2021 it sold a controlling interest to E. Gluck Corporation, a fashion watch business in Little Neck, N.Y. (Ms. Weichselbaum’s family has operated E. Gluck since its establishment in 1956; she is its chief executive).

The idea behind the partnership of the companies was to combine WITHit’s technology and experience in product development with E. Gluck Corporation’s design and production network, and to push E. Gluck beyond just watches. Mr. Devaney noted that future plans included a similar Band Candy concept for AirPods and new Band Candy sliders and charm sets.

Adam Gelnick, the chief financial officer at E. Gluck, said moving from watches to developing the Band Candy line had been an exciting opportunity — to go from “something that we always defined as a timeless product to a product of our time.”