Frsky R-XSR receivers are now coming installed with ACCESS firmware. To bind with ACCST only radios, a firmware update is required. Firmware can be found here: https://www.frsky-rc.com/r-xsr/ (Select history firmware download for ACCST 1.0 firmware)
FrSky ultra mini receiver R-XSR is the evolution of FrSky full range XSR receiver. The R-XSR is a standalone receiver with all the functions of XSR, in addition, it's almost 1/3 size and 1/3 weight of XSR receiver. Moreover, there redundancy function is integrated into this tiny receiver ensures the security, and the IPEX connector makes it more convenient to replace antennas.
Specifications
Dimension: 16*11*5.4mm (L*W*H)
Weight: 1.5g
Number of channels: 16CH (1-16CH from SBUS channel, 1~8CH from CPPM channel)
Operating Voltage Range: 4~10V
Firmware Upgradable
Compatibility: FrSky X Series modules and radios in D16 mode
If you are looking for a D16 capable receiver, this is a nice choice for a small quad or airplane. Full telemetry and RSSI is available on a channel if you want to display it in an OSD. Price is still reasonable on HeliDirect and their service is second to none.
R
Rdd
Accessories
Nice add on
Q
Quality
Exactly what I ordered. 
J
Joseph M.
Great little receiver
These are my go to receiver for quads, except when I need ultra long range, then I use crossfire. You can't beat them for the price and the range is excellent for 2.4GHz.
L
Leon
small and full telemetry SBUS receiver from FrSky. FrSky R-XSR 2.4GHz 16CH ACCST Micro Receiver less than 2 grs , I already have more than 6 of theses receivers without ever a single failure
S
Skyler
Reliable and lightweight
Best Frsky receiver for 2.4ghz in my opinion. It's very lightweight and the diversity is great. I get amazing range with this thing.