Just spotted these - perhaps everyone knows already. Should be longer lived and never need greasing.
[ame]http://www.amazon.com/gp/product/B010C7N85O/ref=pd_lpo_sbs_dp_ss_3/181-8760455-4139101?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=lpo-top-stripe-1&pf_rd_r=0T386WNHBW7VTBK2HF0E&pf_rd_t=201&pf_rd_p=1944687662&pf_rd_i=B00MON6DAC[/ame]
[ame]http://www.amazon.com/gp/product/B010C7N85O/ref=pd_lpo_sbs_dp_ss_3/181-8760455-4139101?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=lpo-top-stripe-1&pf_rd_r=0T386WNHBW7VTBK2HF0E&pf_rd_t=201&pf_rd_p=1944687662&pf_rd_i=B00MON6DAC[/ame]