Think of it as Black Friday in July. Tuesday, July 12, is Amazon’s (AMZN) second annual Prime Day, and the company is offering deals on 100,000 items over 24 hours. New deals will be introduced as often as every five minutes. Here’s a rundown of what to expect.

Starting at midnight PT/ 3 a.m. ET, Amazon is offering promotions exclusively to its Prime members. Consumers who aren’t Prime members who want to get in on the deals can sign up for a free 30-day trial. This will be the Seattle retailer’s second Prime Day; last year the company reported 34.4 million items sold, which translates to 398 items per second.

There are three different kinds of deals that will be available: lightning, spotlight and savings and deals. The lightning deal, as the name implies, is available for a limited time, a few hours at most. Spotlight deals are ones Amazon highlights as the best sales of the day. Savings and deals are promos that will be available all day. You can find the deals online or on the Amazon Shopping mobile app.

Prime members who have an Echo device can get $10 off their first purchase of at least $20 if they snag a deal using their voice.

Members in countries that currently offer Amazon Prime memberships — the US, UK, Spain, Japan, Italy, Germany, France, Canada, Belgium and Austria — will have access to these sales.

For extra hype, Amazon has been offering “countdown deals” for Prime members between July 5 and July 11 — Monday’s include vacuums, protein powders and fitness tracking devices.

What kinds of deals can you expect?

Despite Amazon calling last year’s Prime Day a huge success, many customers took to social media to express dissatisfaction over what some saw as low-quality, seemingly random products, like thermal laminators and 24-inch shoehorns. One likened the day to a “Marshall’s clearance bin.”

That’s why this year Amazon is offering a lot more stuff. “Following last year’s record sales, we have dramatically increased the inventory behind many deals,” said Greg Greeley, vice president of Amazon Prime, in a statement.

Specifically highlighting TVs, headphones, slow cookers and vitamins, the company says you’ll be able to get your hands “on things you want, things you need, and everything in between.” Amazon will offer nearly twice the number of TVs compared to Black Friday and Cyber Monday combined.

According to the company, toys, mobile device cases, and pet products were hot sellers in the US last year. To cater to that interest, Amazon will be offering toy deals “nearly all day.” The retailer says it’s also adding sellers: twice as many small business sellers will be participating globally.

The case for Prime

Amazon Prime costs $99 a year. The main draw is the unlimited free shipping option (there’s unlimited free two-day shipping on more than 20 million items, unlimited free same-day delivery on a million items in 14 metro areas). For non-Prime members, the minimum purchase amount to get free shipping is $49.

But there’s more value to Prime than just free shipping on your Amazon orders. Prime is also great for streaming junkies — especially with the emergence of popular original shows like “Transparent,” “Catastrophe,” “The Man in the High Castle,” and “Mozart in the Jungle.”

Prime members get unlimited, ad-free access to more than a million songs as well as curated playlists, and unlimited photo storage in Amazon’s Cloud Drive. Plus, you can borrow books from the “Kindle Owners’ Lending Library” and share them with another adult in your family.

More competition

Amazon won’t say how many Prime members it has, but the latest estimate from Consumer Intelligence Research Partners (CIRP) pegs the figure at 63 million subscribers, 19 million of them joined since last July.

More shoppers tried Prime worldwide on Amazon Prime Day than any other day in Amazon’s history, according to the company. And CIRP found that 73% of 30-day trial subscribers do end up paying for the year of membership.

In an effort to compete with Amazon, Walmart (WMT) is getting generous in the unlimited shipping category. On Monday it announced a new program, ShippingPass, that offers free unlimited two-day shipping. It costs $49 a year, half as much as the cost of Prime (but you’re really only getting a fraction of what Amazon Prime has to offer).

Prime Day is most similar to Alibaba’s (BABA) Singles’ Day. Held every November, Singles’ Day was originally a joke celebration for single people in China. Alibaba capitalized on this in 2009 to make it a shopping bonanza for all, by offering flash promotions and steep discounts. Last year, the Chinese e-commerce giant said the total value of goods transacted on that day was $14.32 billion.

The bottom line is Prime Day is great if you already have a membership, but you shouldn’t be joining for a day of deals alone (or if you do, try the 30-day trial and if you don’t become a die-hard Prime fan, remember to cancel the membership before the fees hit). As one saying goes, if you didn’t see, you wouldn’t buy it.

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