A solution for most scenarios and antenna connectors, officially called "Nooelec SMA Adapter Connectivity Kit", a plastic box with lots of shiny connectors:
Costs US$19.95 on official Nooelec website or on Amazon USA, had it in a week from the States to Europe for free as a review sample (disclaimer).
Any radio lover who needs to connect different bits and pieces to radio receivers, accessories, paraphernalia and antennas, or vice versa, because the industry still haven't settled on one connector standard.
Sturdy closeable plastic box with eight compartments and fold-down latch, all 100 kg / 220 lbs of yours stood on it one-legged and didn't budge, carried box around for weeks and didn't open once. Internal dividers enable custom partitioning, no idea what purpose flimsy bit with hole serves, maybe if you're climbing a sheer wall and want to attach it to a rope?
Nooelec.com sign on top is mentally reassuring, writing what's what on each compartment might be a good idea - I had a rough idea what purpose a particular connector serves, but neighbor Jane wouldn't have a clue.
All connectors end up in SMA male termination, which is the most common on quality SDR gear, so it's possible to connect any equipment, such as Nooelec SMArt / rtl-sdr.com v.3 / SDRPlay RSP / AirSpy / whatever with SMA female sticking out.
Female N-connector: Chunky pro level equipment uses N-connectors, like transmitters and antennas in the kiloWatt range.
Female F-connector: Standard for TV in the USA, satellite and cable TV and internet modems in Europe, widespread around the world.
Great fan of this standard as easiest to assemble at home, plugs are cheap as chips at any electrical shop.
SO 239: Relic from WW2, oldtimers with tabletop HF transceivers or CB equipment might need it. Not using it at the moment, love the fact it's included, because any CB magnetic mount (or similar gear found for cheap) could be easily utilized.
BNC adapter: also known as bajonet mount, push and twist, for instance, use with scanner antennas (in image below).
For an at-home setup, CCTV T-junctions and coax notches based on BNC connectors work extremely well as a poor man's bandpass filter.
MCX: SMA Male to MCX Female, so if you got an old antenna mount, it can be used with the latest gear:
PAL: TV standard in Europe and in many parts of the world - use store-bought antennas easily.
PAL is extremely easy to work with due to size and no-brainer one-hand push-in movement.
RP SMA: RP means Reverse Polarity, easier to explain with an image:
Reverse Polarity often catches out beginners as they wish to use WiFi antennas with dongles without any success - inserting a 4mm coax center inbetween is a solution, but the proper adapter will be less hassle:
Male SMA barrel: Standard to connect any SMA to any other SMA gear, priceless when you want two otherwise useless doorstops to work in harmony.
Tried all connectors with multiple antennas / LNAs / receivers and all functioned flawlessly. Personal sidenote: I use Nooelec connectors for over two years and not one malfunction ever, so got no doubts this kit will serve me into 2020 easily.
Barrel adapters, like the contents of this kit, have less points of failure and less signal loss due to no coax cable used. Pigtails are more flexible, easier to screw on / off, but cost more.
Depends on what you wanna do: for a fixed setup when components are not moved around, like ADS-B testing, I prefer barrel connectors. For on-the-road use, pigtails are clear winners due to less stress on connectors and PCB mounting points.
Rtl-sdr.com offers a 6-piece set for $15 without a box or quite a few alternatives, haven't tested them, so can't comment. Seriously doubt that these connectors / adapters are markedly different from other offerings on the market, try searching eBay for "SMA adapter kit", results will look identical with prices hovering around the 1.50- 3 dollar mark per piece with shipping from China, or six to eight piece kits for around 10-15 USD can be had.
8 adapters in a plastic box for $20 from a trusted brand is reasonable.
Look into what you need, examine photos above to identify you dongle / antennas / gear, think about future prospects.
Yes. Flexibility is the name of the game, especially if you've amassed an antenna connection, and it's eventually cheaper and easier to have one box that enables otherwise useless bits and pieces to function.
Costs US$19.95 on official Nooelec website or on Amazon USA, had it in a week from the States to Europe for free as a review sample (disclaimer).
Who is this for?
Any radio lover who needs to connect different bits and pieces to radio receivers, accessories, paraphernalia and antennas, or vice versa, because the industry still haven't settled on one connector standard.
What you get

Nooelec.com sign on top is mentally reassuring, writing what's what on each compartment might be a good idea - I had a rough idea what purpose a particular connector serves, but neighbor Jane wouldn't have a clue.
All connectors end up in SMA male termination, which is the most common on quality SDR gear, so it's possible to connect any equipment, such as Nooelec SMArt / rtl-sdr.com v.3 / SDRPlay RSP / AirSpy / whatever with SMA female sticking out.
Female N-connector: Chunky pro level equipment uses N-connectors, like transmitters and antennas in the kiloWatt range.
Female F-connector: Standard for TV in the USA, satellite and cable TV and internet modems in Europe, widespread around the world.
Great fan of this standard as easiest to assemble at home, plugs are cheap as chips at any electrical shop.
SO 239: Relic from WW2, oldtimers with tabletop HF transceivers or CB equipment might need it. Not using it at the moment, love the fact it's included, because any CB magnetic mount (or similar gear found for cheap) could be easily utilized.
BNC adapter: also known as bajonet mount, push and twist, for instance, use with scanner antennas (in image below).
For an at-home setup, CCTV T-junctions and coax notches based on BNC connectors work extremely well as a poor man's bandpass filter.
MCX: SMA Male to MCX Female, so if you got an old antenna mount, it can be used with the latest gear:
PAL: TV standard in Europe and in many parts of the world - use store-bought antennas easily.
PAL is extremely easy to work with due to size and no-brainer one-hand push-in movement.
RP SMA: RP means Reverse Polarity, easier to explain with an image:
Reverse Polarity often catches out beginners as they wish to use WiFi antennas with dongles without any success - inserting a 4mm coax center inbetween is a solution, but the proper adapter will be less hassle:
Male SMA barrel: Standard to connect any SMA to any other SMA gear, priceless when you want two otherwise useless doorstops to work in harmony.
Reliability
Tried all connectors with multiple antennas / LNAs / receivers and all functioned flawlessly. Personal sidenote: I use Nooelec connectors for over two years and not one malfunction ever, so got no doubts this kit will serve me into 2020 easily.
Barrel or pigtail?
Barrel adapters, like the contents of this kit, have less points of failure and less signal loss due to no coax cable used. Pigtails are more flexible, easier to screw on / off, but cost more.
Depends on what you wanna do: for a fixed setup when components are not moved around, like ADS-B testing, I prefer barrel connectors. For on-the-road use, pigtails are clear winners due to less stress on connectors and PCB mounting points.
Competitors and value for money
Rtl-sdr.com offers a 6-piece set for $15 without a box or quite a few alternatives, haven't tested them, so can't comment. Seriously doubt that these connectors / adapters are markedly different from other offerings on the market, try searching eBay for "SMA adapter kit", results will look identical with prices hovering around the 1.50- 3 dollar mark per piece with shipping from China, or six to eight piece kits for around 10-15 USD can be had.
8 adapters in a plastic box for $20 from a trusted brand is reasonable.
Look into what you need, examine photos above to identify you dongle / antennas / gear, think about future prospects.
Would I spend my own money on this?
Yes. Flexibility is the name of the game, especially if you've amassed an antenna connection, and it's eventually cheaper and easier to have one box that enables otherwise useless bits and pieces to function.