BRENT, THIS IS WHAT I WAS LOOKING FOR THANK YOU .now things are staring to clear up , I was always wondering why the dive tables were so much differant for rebreathers. as far as training ,yes yes I agree 100% , the reason for the question ??? was to ferther this process for me .after all I thought that was what this site was all about , anyway I'll bet a lot of newbees have thought about this same question and were afraid to ask, so I'am the dumb bastard that just had to ask LOL. for myself I find it hard to go much below 40m and have not done so in many year ,the reason I became interested in rebreathers is size & weight ,a whole weekends diving in a 40# package.the training that I 've looked at usually comes with a manufactors uinit that I don't like, no names here please, ever one here has his or her preferrance ,as for homebuilt & training they don't go well together when one goes into the LDS and I'am not talking church, well maybe for some ??? the other Is I have the shop tools to do the job & the ability & while I'am not in any way a excelent machinst ,I can . reason 3 $$$$$ most manufactured rebreather cost more than I paid for my intire boat motor sails . thanks to all for the help , and like the man says...I'll be back see ya.