Non-fungible tokens, or NFTs – the cryptographically rare digital items CryptoKitties made famous – are so new, they're challenging for prospective sellers to price.

That's according to Devin Finzer, co-founder of OpenSea, a startup billed as an "eBay for CryptoKitties," but that is aiming to stake its claim more broadly as a platform for blockchain-based collectibles.

This issue in mind, the company, backed by investors like Founders Fund and Coinbase Ventures, is announcing a new feature Monday called "bundles," which allows users to sell multiple NFTs at a single, fixed price.

Finzer told CoinDesk:

Like sales of individual items, bundles can either be sold at a fixed price or auctioned.

In a blog post, the OpenSea team highlighted how the feature will add to the maturing ecosystem surrounding crypto collectibles, one of the more new and still experimental use cases for the technology.

"At OpenSea, we believe a big driver of these new economies is a robust, easy-to-use toolset for buyers and sellers," the blog post continued. "Bundling is one of those tools."

Bundling – through bulk sales, grab bags and other types of collections – has existed for a long time in markets for analog collectibles.

For instance, on eBay, collectors can sell more than one comic book at a time, since if bundling wasn't available, it wouldn't be worth it to try an offload anything except the most popular issues. Owners can then recoup some value from the less sought-after items by selling them in batches.

Similarly, Finzer told CoinDesk that he's spoken to users who have crypto collectibles that aren't even worth the ethereum gas it would cost to sell them individually. As such, the ability to sell groups of items is helpful.

Further, some new crypto projects are generating categories of NFTs that might only make sense to sell in bundles. For example, Finzer told CoinDesk how the bundle feature could help one of its partners, Etheremon, which recreates the Pokemon Go experience.

"Users can earn special crystals and power-ups by going on quests," Finzer said. "Since each user might have a ton of those items, bundling is really helpful."

Any new ERC-721 project will be able to sell bundles on OpenSea. For companies using OpenSea's API to put items into its marketplace, bundles will work through that interface as well.

Plus, OpenSea respects custody; users can play with bundled items on sale up to the moment they transfer ownership.

Since late September, some users have actually been able to list bundles. (During this beta phase, OpenSea users made 137 such listings).

MLB Crypto Baseball, a version of fantasy baseball where players own NFTs representing real-world players that they assemble into teams, is a prime example of where bundles could be beneficial. In that way, sellers can make bundles that will allow newbies to get started easily.

Speaking to CoinDesk, Finzer said, "There's also recently been a lot of excitement about the bundling feature in the MLB Crypto Baseball Discord. There's already a bundle listed with three entire MLB baseball teams in it."

Plus, this decentralization of game pieces can open up even more possibilities.

In fact, a user can now sell a selection of NFTs from across multiple games. As of this writing, there is a bundle on sale mixing NFTs from decentralized applications CryptoKitties, ETHTown and War Riders.

In this way, OpenSea expects users will explore even more strategies, like including one slightly more valuable item in a group to entice people to buy a whole group of items.

Image courtesy of Etheremon