X on Friday unveiled a $16-a-month subscription plan allowing users who pay more to get the biggest boost for their replies posted at the platform formerly known as Twitter.

The "Premium+" plan is ad-free and designed to provide "the largest reply boost" at X, the company said in a post.

The plan builds on features offered in a Blue subscription plan costing $3 monthly and a Premium Plan priced at $8 monthly, according to X.

Listed features of Premium+ include a blue tick next to names in profiles along with "a visible ID verification label," according to X.

The platform recently started charging new users in New Zealand and the Philippines for basic features such as posting messages in a trial aimed at reducing spam.

Musk has suggested charging all X users, but the idea was widely panned. Industry analysts said it would make X even less appealing to advertisers.

Musk has made a number of controversial changes to the social media firm's management and product since he acquired Twitter a year ago for $44 billion. 

In the days after his purchase, Musk quickly fired many Twitter executives and took the publicly traded company private.

He also laid off most of the San Francisco-based company's workers, cutting ranks to fewer than 1,500 from 8,000.

In the months following his takeover, Musk gutted content moderation, restored accounts of previously banned extremists, and allowed users to purchase account verification, helping them profit from viral — but often inaccurate — posts.

Musk defended such changes in the name of free speech.

Over the past year, the platform's advertising business partially collapsed as marketers soured on X.

Musk started charging for features once free at Twitter, such as blue tick marks originally intended as badges of authenticity, in an effort to make money from subscriptions. 

X is tinkering with video and audio calling at the platform formerly known as Twitter, according to a recent post by Musk.

Musk in July rebranded Twitter as X, saying it would become an "everything app" inspired by China's WeChat that would allow users to socialize as well as handle their finances.