3.5mm Mono Jack line socket, with solder contacts.  Low cost part useful part where cable runs need to be extended.  Plastic cover with cable strain relief. 

The price of £1.90 shown is for a pack of 10.  Also available are packs of 25 and 100.  This also shows the additional cost in brackets. price (each): 10+ £0.19     25+ £0.17     100+ £0.14 price (total):  10+ £1.90     25+ £4.25     100+ £14.00