Upgraded my network from 10gig to 25gig, so selling my 10gig stuff. These are offerI bi directional adapters and come in pairs. They allow you to use just one side of an LC cable, thus you can create bonded 20gig links with two pairs and a single LC cable (how i ran them).
Works great, i have 4 pairs, max discount if you buy all four pairs.
10Gtek a Pair of 10G SFP+ offeri Transceiver, 10GBASE-BX20-U 10GBase-offerI 1270nm/1330nm, DOM Simplex LC SMF Module for Ubiquiti UniFi, up to 10-20km

10Gtek's offerI 10G SFP+ Transceiver used in optical communications for both telecommunication and data offerirectional communications applications.

Application for Ubiquiti products
10GBASE-offerI offerirectional sfp+ Optic, up to 20km over single LC
Wave length: Up: TX1270nm/RX1330nm; Down: TX1330nm/RX1270nm
Data Rate: 10Gbps
Reach: 10~20km
Form Factor: SFP+
Fiber Type: SMF
Tx Power(dBm): 1~5dBm
Rx Sens.(dBm): <-15dBm
Temp.(°C): 0~70