Frequently asked questions

Five things, each checked against your machine: the generation (DDR4 and DDR5 modules each fit only their own slots), the form (SODIMM for laptops, full-size DIMM for desktops and servers), the type (registered or unbuffered, ECC or not), the capacity and module count, and the speed in MT/s (a faster module runs at your machine's speed, so pay only for the speed it uses). A part number in the listing confirms the module's generation, form, type, size and speed at once; the title and eBay's quantity say how many modules the price buys.

RAMindex reads the capacity, module type, speed and ECC from each title and shows them as columns on every row, beside eBay's own condition, so you compare like with like. Start from laptop RAM, desktop RAM or all RAM and narrow the table with Filter options.

Read it in three layers: the title is the seller's summary, the item specifics under the photos are the structured version, and a photo of the label on the actual module is the record. When they disagree, trust the label; what a good listing photo shows is in our used-RAM guide.

Then check what the price buys. "2x16GB" is one 32GB kit of two modules; "lot of 10" is usually ten modules, though some sellers write their stock that way and price one, so read the quantity on eBay's page. RAMindex works out the total capacity of each listing and divides the price by it, so single modules, kits and lots line up on one scale, price per GB. Shipping is shown beside each price, and eBay's page always has the live price.

• DDR3, DDR4, DDR5: The generation. Each fits only its own slots: how the generations differ.
• DIMM, SODIMM: Full-size modules for desktops and servers, and short ones for laptops and mini PCs.
• 3200 MT/s, "3200MHz", PC4-25600: One speed written three ways: the data rate, the way most sellers write it, and the bandwidth rating. MHz or MT/s?
• CL22: CAS latency, the wait in clock cycles; lower is quicker at the same speed. CAS latency explained
• 1Rx8, 2Rx4: Ranks and chip width: how many sets of chips a module has, and how wide each chip is. They matter most in servers. Ranks explained
• ECC: Error-correcting memory, for servers and workstations. ECC or non-ECC?
• RDIMM, UDIMM, LRDIMM: Registered, unbuffered and load-reduced. Desktops and laptops take unbuffered modules; most servers take registered ones. Server RAM in a desktop?

Find the part number on the label in the photos: Samsung's begin with M, SK hynix's with HM and Micron's with MT. Look it up in the part number index, where each part has a page with its specification and its listings on eBay. When a title and its part number disagree, the part number is right; decoding a part number shows how.

Then check your machine: RAM by processor gives the memory type, speed and maximum each processor supports, server RAM covers servers model by model, and What RAM is compatible with my computer? walks through it step by step. If the label is not pictured, ask the seller for a photo before you buy.

Mostly because memory as a whole became expensive. The three companies that make nearly nine-tenths of the world's DRAM have given their wafers to AI data centers first, so prices for ordinary memory rose steeply from the second half of 2025, and a used module is sold beside new ones, so its price is set against theirs. Older generations add scarcity: the makers sent end-of-life notices for DDR4 in 2025, nothing replaced that supply, and the squeeze ran down to DDR3 and DDR2.

Trends shows how prices per GB are moving now, by generation, and Why is RAM so expensive in 2026? covers the shortage and when it may end.

Each price is what one seller asks, so the useful test is how it compares with every other listing of the same thing. That is what RAMindex measures: each table ranks Buy It Now listings by price per GB, cheapest first, with the shipping shown beside each price. The order is arithmetic alone, and no seller can pay to rank higher.

Narrow a table to your exact module with Filter options: the line under its heading gives the cheapest Buy It Now price per GB, and the Price per GB chart gives the median, which is the going rate. The part number index gives each part a page with its listings side by side, Trends shows the typical price per GB over time, and eBay's own page always has the live price.

Because the module is the same but the offer is not. Sellers differ in condition and testing, in what they charge for shipping, in the return window they give, in where they ship from, and in how many they have to sell: a recycler with hundreds of pulled modules prices to move them. A listing also keeps its price until the seller changes it, so an older one can sit above or below today's market, and some invite offers.

Every RAMindex row shows the condition, the shipping and the country a module ships from. Each part in the part number index has a page that gathers its listings together, and Prices by country compares what memory costs when it is listed in each country.

It depends on what you buy. Used memory, older generations and server modules are easiest to find on eBay, because recyclers and upgraders sell there what comes out of retired laptops, desktops and servers, and many are hard to find new at all. For a new kit, price a store too: in 2026 the cheapest store kits have at times matched or beaten eBay's typical price for the same kit, and they come with the maker's warranty.

Compare by price per GB: divide a shop's price by the kit's capacity, narrow the matching RAMindex table, such as DDR5 or DDR4, to the same form, size and condition with Filter options, and set the shop's figure against the cheapest price per GB under its heading and the median in its Price per GB chart. The tables show eBay's shipping beside each price, and a shop's price often includes delivery. Should I buy RAM now or wait? covers timing.

On eBay, New is sealed and unused; Open box is unused but opened; Used has run in another machine, most often pulled from a laptop, desktop or server; the refurbished grades have been restored to working order by the maker, an approved refurbisher or the seller; and For parts or not working is sold for repair or salvage.

Memory has no moving parts and nothing in it is used up in normal use, so a used module that passes a memory test is as good a buy as a new one, and usually costs less. Every RAMindex row shows its condition, and Filter options narrows a table by condition, such as Used. Is it safe to buy used RAM? shows how to test what arrives.

Each seller sets a return policy, shown on the listing beside the shipping: often 30 or 60 days, sometimes none. On top of it, the eBay Money Back Guarantee covers you if a module does not arrive, arrives faulty when the listing did not say so, or is not what the listing described, even when the seller takes no returns. You have 30 days after the actual or estimated delivery date to open a request, or the seller's own return window if that is longer.

A module that works and matches its listing but does not suit your machine falls under the seller's policy alone, so check the fit first. Test memory as soon as it arrives, while the window is open; the return path in our used-RAM guide has the details.