I have a Celestron 16mm Erfle and a 20mm Erfle, both are in like new condition, both have caps. I have the box for the 20mm. I am interested in trading both for 2 of the following eyepieces - TeleVue plossl 26mm, 21mm or 10.5mm (old style - no rubber grip ring). They must be in excellent condition. Please do not contact me to buy the Erfles without a trade. If a trade is not out there I may relist in a few days and sell them outright. I can send a digital photo to anyone with a serious trade offer. I can supplement the trade with a payment to even things out.